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The Pamphlet Collection of Sir Robert Stout: Volume 63

(Part II.) — [Lecture delivered October 16, 1869.]

(Part II.)

[Lecture delivered October 16, 1869.]

I will now proceed to discuss, at greater length, that part of the subject which more especially referred to the effects likely to be produced upon the fauna and flora of this country, by the introduction of competing foreign organisms. In order that you may be able satisfactorily to follow my observations, it will be necessary that I should, in the first place, call your attention shortly to the divisions and classification of the organic world, and the laws which govern its distribution; and, somewhat more fully, to the views page 314 originated by Mr. Darwin, and now generally entertained by naturalists, is regard to the "Origin of Species," for (as you will find in the sequel) I have assumed that many of the principles of action which his theory is intended to elucidate, are directly engaged in producing the changes which I propose to notice, both as having been already effected, and as being likely to ensue in the course of time.

You are all doubtless aware, that organic nature is broadly divisible into two great branches, namely, animal and vegetable life, the study of the former being termed Zoology, and of the latter Botany. It is true, that at the extreme confines of each of these two kingdoms, as we descend from the higher to the lower forms, even this broad distinction is apparently obliterated, and we find, in effect, that naturalists were long in doubt to which of the two kingdoms some of the lowest observed organisms, ought properly to be assigned. This, however, is a matter which little concerns our present enquiry, through it certainly helps to demonstrate the accuracy of that admirable analysis of the organic world, which has lately been exhibited to us by our great physiological writers, and from which we have learnt, not only that the infinite" diversity both of animal and vegetable life which peoples the globe, may all be brought down to the primordial form of a single cell, but also that both may be reduced into, and are, in fact, composed of the same elementary constituents.

It had, however, been known long before reaching this more advanced analysis, that the enormous multiplicity both of animal and vegetable life, could, in each case, be reduced to a few types of construction, and, indeed, the types thus established have constituted the bases of all those system of classification by the elaboration of which we have been enabled to study the organic world in detail.

Looking to the probability that the vegetable kingdom yielded to man his earliest means both of sustenance and shelter, it has been assumed by every writer on Natural History, that it was the first to engage his attention and become his study, and that the necessity of distinguishing between such forms as were useful and such as were injurious, led to the first rude classification of vegetable life. "By placing together individuals apparently identical in form (says Dr. Lindley), and having regard to the uses they could be applied to, species were distinguished, and by applying a similar process to the species themselves, groups analagous to what we now call genera were obtained. The last step was to constitute classes, which were recognized under the well known names of 'grass and herbs yielding seed, and fruit trees yielding fruit.'"

It will not be necessary for me to point out how, step by step, the complete systems of classification now adopted by naturalists were arrived at, how the artificial system of Linnaeus was replaced by the natural systems of succeeding enquirers, until we are gradually reaching a more exact knowledge of the plan of nature, it being sufficient for my purpose to call your attention broadly to those systems, and to the circumstance that, in every case, virtually terminate with what is called "species."

The animal kingdom has been primarily divided into two great Sub-kingdoms or Provinces, namely, the Vertebrata and the Invertebrata, each of which has been again subdivided into classes, orders, families, and species.

The vegetable kingdom has also been primarily divided into two sub-kingdoms, namely, into asexual or flowerless, and sexual or flowering plants, each comprising a number of distinct classes, orders, genera, and species. With the latter term indeed, whether in the Animal or Vegetable Kingdoms, classification proper has been supposed to end, although all systematists have recognized the existence of varieties, even in a state of nature.

Now it might be supposed, looking more particularly to our recent page 315 great advance in knowledge of the physiology and anatomy both of animals and plants, that, for purposes of classification, there would be little difficulty in defining the term "species" as applied to any particular class or group of organisms, but this is far from being the case, for we find, that the most acute and diligent enquirers, after careful study of the question, have acknowledged that this term can only be applied arbitrarily and for the sake of convenience merely, to some set of individuals closely resembling each other, and that in its necessary application by systematists it does not essentially differ from the term "variety" which, in comparison with mere individual differences, is usually given quite as arbitrarily to forms somewhat less distinct and more fluctuating.

This point has been made the subject of most elaborate investigation by Mr. Darwin, in his volume on the "Origin of Species," in which he has brought together a great mass of facts to prove that all classes of organisms exhibit a greater or less degree of variability, and to show the consequent difficulty of giving any conclusive or satisfactory definition of the term "Species,"—the general conclusions he arrived at being thus stated,—"Finally, then, varieties have the same general character as species, for they cannot be distinguished from species—except, firstly, by the discovery of intermediate linking forms, and the occurrence of such links cannot affect the actual characters of the forms which they connect; and except, secondly, by a certain amount of difference, for two forms, if differing very little, are generally ranked as varieties, notwithstanding that intermediate linking forms have not been discovered; but the amount of difference considered necessary to give to two forms the rank of species, is quite indefinite. In genera having more than the average number of species, in any country, the species of these genera have more than the average number of varieties. In large genera the species are apt to be closely, but unequally allied together, forming little clusters round certain species. Species very closely allied to other species, apparently have restricted ranges. In all these several respects the species of large genera present a strong analogy with varieties. And we can clearly understand these analogies, if species have once existed as varieties, and have thus originated : whereas, these analogies are utterly inexplicable if each species has been independently created.

"We have, also, seen, that it is the most flourishing or dominant species of the larger genera which, on an average vary most; and varieties, as we shall hereafter see, tend to become converted into new and distinct species. The larger genera thus tend to become larger; and, throughout nature, the forms of life which are now dominant, tend to become still more dominant by leaving many modified and dominant descendants. But, by steps hereafter to be explained, the larger genera also tend to break up into smaller genera. And thus, the forms of life, throughout the Universe, become divided into groups subordinate to groups."

Flourens, in his paper on "La Quantité de vie sur le Globe," also tells us, "that every species manifests two tendencies, namely, a tendency to vary and a tendency to transmit to succeeding generations the acquired modifications;" and he, properly, observes, "that if the acquired variations and modifications of each generation could not be transmitted to its descendants, such variations and modifications would remain mere individual traits, and would never become the characteristics of a race." Flourens, however, does not appear to have seen the full effect of these views as to the variability of species, for he assumes that such variations only affect what he terms "superficial characteristics," and that they are at all times easily detected, whilst he urges that "the unity, identity, and reality of a species is always determinable by the presence or absence of the more deep seated characteristic of continuous fecundity."

page 316

In order to illustrate the difficulty referred to by Mr. Darwin, I will call your attention to some instances in nature.

Experiment has shown that the Zebra, the Hemionus, the Ass, and the I Horse, can mutually produce young, but that their produce, notwithstanding I certain exceptional instances of further fertility which have been sufficiently well authenticated, cannot perpetuate themselves, and yet no naturalist holding a position of eminence at the present day, would venture to deny that these four races of animals have all descended from common ancestors.

Here, then, we have an example of very limited divergence in outward form, accompanied by great limitation in fecundity, and naturalists may, notwithstanding their admitted descent from common ancestors fairly claim to treat each of these animals as having reached the position of a separate species.

With the dog, on the other hand, although the external difference between many forms, as, for example, the Bull dog, the Turnspit, and the Greyhound, are far greater and more striking than those which we observe between the Horse, the Ass, and the Hemionus, yet the former are always perfectly fertile in interbreeding, and the cross-breeds perpetuate themselves. Here then we have an example of considerable divergence in outward form, in the "superficial characteristics" of Flourens, without any apparent interference with fecundity, and, yet, in this case, although naturalists have also I arrived at the conclusion that all existing varieties of the dog are descended from common ancestors, they also treat each of these animals as a separate species.

If, therefore, continuous fecundity were the essential characteristic in the determination of "species," then the Horse, the Ass, and the Hemionus ought to be treated as separate species, whilst the Bull dog, and the Greyhound, and all the other innumerable and peculiar forms of Dog found in every corner of the globe, ought only to be ranked as varieties of one species.

Such an adherence to any arbitrary rule is, however, unnecessary for purposes of classification, though it bears strongly upon other points in the theory propounded by Mr. Darwin to which I propose hereafter to call your attention. But it is not only to animal life that the foregoing observations extend. Although more difficult to understand in their application, the same rules must be adopted in dealing with the classification of vegetable organisms Take, for example, plants belonging to the natural order Composite which includes the Daisy, the Groundsel, and other allied forms. Here on the table you have four specimens, very similar in outward form, and at least as closely allied in essential points of structure as the Horse and his congeners.

Now, although we have not yet attempted to ascertain experimentally whether these four forms would produce cross-breeds, I think few naturalists would for one moment suppose that they would. If this be so, then we have here an example of still greater divergence in fecundity, whilst we have no difficulty in believing that these several forms, as well as all other plants belonging to the same order, had a common origin. Indeed it would be easy to bring together numberless examples from the book of nature, of incomplete fecundity with slight divergence in outward form or general structure; of complete fecundity with great divergence in outward form; and complete sterility with great similarity in most of those characteristics, which are used by naturalists for purposes of classification, while, at the same time, we should have little hesitation in admitting the descent of all the species of each class, from common ancestors. I will merely add further, that whilst all great naturalists admit that it is quite chimerical to suppose that we can construct any arrangement which shall be an absolutely correct expression of the plan of nature, yet they also allow that we can, by carrying into effect with care and page 317 skill certain well recognized principles, construct what may fairly be tern ed a natural system.

In such a system groups of species are collected into genera, groups of genera into orders, and groups of orders into classes; each order comprising a number genera distinct from those of the others, but which, nevertheless, are distinguished by certain general characters different from those of any other orders of plants, characters, too, which are preserved through every existing modification of form.

I have thus shown you that the organic world is primarily divided into pro great kingdoms; that each of these is subdivided into classes, orders, genera, and so-called species; and that every species is held to possess two leading tendencies, the one to vary, and the other to accumulate such variations there profitable, by transmitting to its descendants the modifications resulting from variation. I now purpose, in the next place, to call your attention shortly to certain observed facts in relation to the geographical distribution of animals and plants.

The Abbé Domenech has observed that "if Eden were the birthplace of mankind, it certainly was not the birthplace of the whole animal and vegetable creation, for," he says, "the works of God invariably bear the witness of Divine Wisdom, and to have created in Eden the Reindeer of Lapland, the Lama of Peru, the Kangaroo of Australia, and the Ostrich of the Sahara, would have been as useless as to people the coasts of Tyre and Sidon with the Whale of Greenland, the Tortoise of the Gulf of Mexico, and with fishes which only live in Intertropical and Hyperborean regions."

"In considering the distribution of organic life over the globe," says Mr. Darwin, "the first great fact which strikes us is, that neither the similarity nor the dissimilarity of the inhabitants of various regions can be accounted for by their climatal and other physical conditions. Of late, almost every author who has studied the subject, has come to this conclusion. The case of America alone would suffice to prove its truth; for, if we exclude the northern parts where the circumpolar land is almost continuous, all authors agree that one of the most fundamental divisions in geographical distribution is that between the New and Old Worlds; yet if we travel over the vast American Continent, from the central parts of the United States to its extreme southern point, we meet with most diversified conditions; the most humid districts, arid deserts, lofty mountains, grassy plains, forests, marshes, lakes, and great rivers, under almost every temperature. There is hardly a climate or condition in the Old World which cannot be paralleled in the New, at least as closely as the same species generally require; for it is a most rare case to find a group of organisms confined to any small spot, having conditions peculiar in only a slight degree; for instance, small areas in the Old World could be pointed out hotter than any in the New World, yet these are not inhabited by a peculiar fauna or flora. Notwithstandsng this parallelism in the conditions of the Old and New Worlds, how widely different are their living productions!

"In the Southern Hemisphere, if we compare large tracts of land in Australia, South Africa, and Western South America, between latitudes 25° and 35°, we shall find parts extremely similar in all their conditions; yet it would not be possible to point out three faunas and floras more utterly dissimilar. Or again, we may compare the productions of South America, south of latitude 35° with those north of 25°, which consequently inhabit a considerably different climate, and they will be found incomparably more closely related to each other, than they are to the productions of Australia or Africa under nearly the same climate. Analagous facts could be given with respect to the inhabitants of the sea."

The author from whom I have just quoted, then points to certain facts page 318 which bear, in a close and important manner, upon the differences between the productions of various regions, and shows how barriers of any kind which prevent free migration, favour,—under the operation of the laws which he proceeds to point out and elucidate—the production of organisms presenting marked differences from each other, without destruction of those general affinities, which the same species (using this term in the sense now applied to it by advanced systematists) present at different points and stations.

In like manner, Sir Charles Lyell, in the last edition of his "Principles of Geology" calls special attention to the geographical distribution of species and to the causes which affect it, and I cannot do better than quote some passages from that work also. And here I may say, that I have the lea hesitation in using extracts from the writings of such authors as Darwin and Lyell, because it would be impossible for me to convey in more clear and apposite language, the matters involved in these extracts.

Sir C. Lyell says, "Although in speculating on 'philosophical possibilities.' said Buffon, writing in 1755, the same temperature might have been expected, all other circumstances being equal, to produce the same beings in different parts of the globe, both in the animal and vegetable kingdoms, yet it is an undoubted fact, that when America was discovered, its indigenous quadrupeds were all dissimilar to those previously known in the Old World. The elephant, the rhinoceros, the hippopotamus, the cameleopard, the camel, the dromedary, the buffalo, the horse, the ass, the lion, the tiger, the apes, the balloons, and a number of other mammalia, were nowhere to be met with on the new continent; while in the old, the American species, of the same great class, were nowhere to be seen—the tapir, the lama, the pacari, the jaguar, the couguar, the agouti, the paca, the coati, and the sloth.

"These phenomena, although few in number, relatively to the whole animate creation, were so striking and so positive in their nature, that the great French naturalist caught sight at once of a general law in the geographical distribution of organic beings, namely, the limitation of groups of distinct species to regions separated from the rest of the globe by certain natural barriers. It was, therefore, in a truly philosophical spirit that, relying on the clearness of the evidence obtained respecting the larger quadrupeds, he ventured to call in question the identifications announced by some contemporary naturalists, of species of animals said to be common to the southern extremities of America and Africa.

"In order to appreciate the importance and novelty of the doctrine, that separate areas of land and water were the abodes of distinct species of animals and plants, we must look back to the times of Buffon and see in what crude conjectures even so great a naturalist as his illustrious contemporary Linnæus indulged, when speculating on the manner in which the earth may first become peopled with its present inhabitants. The habitable world was imagined by the Swedish philosopher to have been for a certain time limited to one small tract, the only portion of the earth's surface that was as yet laid bare by the subsidence of the primeval ocean. In this fertile spot the originals of all the species of plants which exist on this globe were congregated together with the first ancestors of all animals and of the human race. 'In quâ commode habitaveurit animalia omnia, et vegetabilia lœte germinaveruit.' In order to accommodate the various habits of so many creatures, and to provide a diversity of climate suited to their several natures, the tract in which the creation took place was supposed to have been situated in some warm region of the earth, but to have contained a lofty mountain range, on the heights and in the declivities of which were found to be all temperatures and every climate, from that of the torrid to that of the frozen zone. There are still perhaps some geologists who adhere to a notion once very popular, that there are signs of a page 319 universal ocean at a remote period after the planet had become the abode of living creatures. But few will now deny that the proportion of sea and land approached very nearly to that now established long before the present species of plants and animals had come into being.

"The reader must bear in mind that the language of Buffon, in 1755, respecting 'natural barriers' which has since been so popular, would be wholly without meaning had not the geographical distribution of organic beings led naturalists to adopt very generally the doctrine of specific centres, or, in other words, to believe that each species, whether of plant or animal, originated in a single birthplace. Reject this view, and the fact that not a single native quad-[unclear: paped] is common to Australia, the Cape of Good Hope, and South America, can in no ways be explained by adverting to the wide extent of intervening ocean, or to the sterile deserts, or the great heat or cold of the climates, through which each species must have passed, before it could migrate from one of those distant regions to another. It might fairly be asked of one who talked of impassable barriers, why the same kangaroos, rhinoceroses, or lamas, should not have been created simultaneously in Australia, Africa, and South America? The horse, the ox, and the dog, although foreign to these countries until introduced by man, are now able to support themselves there in a wild state; and can scarcely doubt that many of the quadrupeds at present peculiar to Australia, Africa, and South America, might have continued in like manner to inhabit all the three continents, had they been indigenous in each, or could they once have got a footing there as new colonists."

I might multiply quotations from these and other authors occupying the [unclear: faremost] rank in the scientific world, in order to show that both sea and land may, in the present condition of organic nature in every part of the globe be properly divided into what have been termed distinct Zoological and Botanical Provinces, each occupied by special groups of animals and plants which, however, have been found to exhibit, in each case, a certain amount of coincidence in range of species; and, indeed, it is urged, that no hypothesis resecting the origin of species can possibly be satisfactory, which does not show, in the first place, how species and genera, and ofter larger groups, now range in space in such a manner as to lead to the implication that they have spread from a limited area termed a "centre of creation," until their progress has been stopped either by some physical barrier or other condition hostile to further extension; and which does not account, in the next place, for the restriction of peculiar generic forms to certain parts of the globe.

There is nothing more striking to the naturalist, moreover, than the fact, well determined, that the rules established by observation in regard to the distribution of living organisms are those which have also been found to obtain in regard to fossil forms, and it has thence been fairly argued, and as I believe sufficiently well proved, that the intimate connection observed between the existing and the fossil forms within each particular province points to the certainty that the former are of derivative origin, and are not primordial or independent creations. I am compelled, having regard to the length of a lecture, arbitrarily to limit my observations upon this part of the subject, but I think that even without going into the reasons urged by Mr. Darwin and others, as to the improbability of our being able to identify the actual fossil ancestor of any living species, or to trace its descent through past geological [unclear: ochs,] I have sufficiently shown to you the probability that the forms of life now occupying any particular Zoological or Botanical Province may be looked upon as the descendants of those which have occupied it during past geological periods, and that the differences between the existing and fossil forms are due to the operation of the laws so clearly expounded by Mr. Darwin. Of course in assuming such a probability, time becomes an important factor, and those page 320 who have been accustomed to trust to Usher's chronology, and to look upon our globe, at least, as having been created within a few thousand years, will be utterly unable to accept, because they cannot comprehend, such a hypothesis. But whilst each particular province presents, as I have explained to you, its own peculiar generic forms, we constantly find a large degree of affinity existing between the organic life occupying more extended areas comprising frequently several of such provinces. Upon this point (in special connection with the affinities of the flora of New Zealand) I quote as follows from Dr. Hooker's "Introductory Essay" to his "Flora of New Zealand," as published in 1853:—

"Of all the branches of Botany, there is none whose elucidation demands so much preparatory study, or so extensive an acquaintance with plants and their affinities, as that of their geographical distribution. Nothing is easier than to explain away all obscure phenomena of dispersion by several speculations on the origin of species, so plausible that the superficial naturalist may accept any of them; and to test their soundness demands a comprehensive knowledge of facts, which, moreover, run great risk of distortion in the lands of those who do not know the value of the evidence they afford. I have endeavoured to enumerate the principal facts that appear to militate against the probability of the same species having originated in more places (or centres) than one; but in so doing I have only partially met the strongest argument of all in favour of a plurality of centres, viz., the difficulty of otherwise accounting for the presence of two widely sundered localities of rare local species, whose seeds cannot have been transported from one to the other by natural causes now in operation. To take an instance, how does it happen that Edwardsia grandiflora inhabits both New Zealand and South America? or Oxalis Magellanica both these localities and Tasmania? The idea of transportation by aerial or oceanic currents cannot be entertained, as the seeds of neither could stand exposure to the salt water, and they are too heavy to be borne in the air.

"Were these the only plants common to these widely sundered localities, the possibility of some exceptional mode of transport might be admitted by those disinclined to receive the doctrine of double centres; but the elucidations of the New Zealand Flora has brought up many similar instances equally difficult to account for, and has developed innumerable collateral phenomena of equal importance, though not of so evident appreciation. These, which all bear upon the same point, may be arranged as follows :—
1.Seventy-seven plants are common to the three great south temperate masses of land, Tasmania, New Zealand and South America.
2.Comparatively few of these are universally distributed species, the greater part being peculiar to the south temperate zone.

"There are upwards of 100 genera, sub-genera, or other well marked groups of plants entirely or nearly confined to New Zealand, Australia and extra-tropical South America. These are represented by one or more species in two or more of these countries, and they thus effect a botanical relationship or affinity between them all, which every botanist appreciates.

"4. These three peculiarities are shared by all the islands in the south temperate zone (including even Tristan d'Achuna, though placed so close to Africa), between which islands the transportation of seeds is even more unlikely than between the larger masses of land.

"The plants of the Antarctic islands which are equally natives of New Zealand, Tasmania, and Australia, are almost invariably found only on the lofty mountains of these countries."

The author then points out certain conclusions, to which he was at that time forced by a consideration of the facts involved in the distribution of the plants composing the New Zealand Flora, and proceeds as follows:—

"It was with these conclusions before me, that I was led to speculate on page 321 the possibility of the plants of the Southern Ocean being the remains of a flora that had once spread over a larger and more continuous tract of land than now exists in that ocean; and that the peculiar Antarctic genera and species may vestiges of a flora characterized by the predominance of plants which are mow scattered throughout the southern islands. An allusion to these speculations was made in the 'Flora Antarctica,' where some circumstances connected with the distribution of the Antarctic islands were dwelt upon, and their resemblance to the summits of a submerged mountain chain was pointed out; but beyond the facts that the general features of the flora favoured such a view, that the difficulties in the way of transport appeared to admit of no other solution, and that there are no limits assignable to the age of the species that would make their creation posterior to such a series of geological changes as should remove the intervening land, there was nothing in the shape of evidence by which my speculation could be supported. I am indebted to the invaluable labours of Lyell and Darwin, for facts that could alone have given countenance to such an hypothesis; the one showing that the necessary time and elevations and depressions of land need not be denied; and the other, that such risings sinkings are in active progress over large portions of the continents and [unclear: mans] of the Southern Hemisphere. It is to the works of Lyell that I must refer for all the necessary data as to influence of climate being dependent on geological change. In the 'Principles of Geology' these laws are proved to be of universal application, and amply illustrated by their being applied to the [unclear: dation] of difficult problems in geographical distribution. It follows from what is there shown, that a change in the relative positions of sea and land has occurred to such an extent since the creation of still existing species, that we have no right to assume that the plants and animals of two given areas, however isolated by ocean, may not have migrated over pre-existing land between them. This was illustrated by an examination of the natural history of Sicily (where land-shells, still existing in Italy, and which could not have crossed the Straits of Messina, are found imbedded on the flanks of Etna, high above the sea-level), regarding which Sir Charles Lyell states that most of the plants and animals of that island are older than the mountains, plains, and rivers they now inhabit."

You will, then, observe that although New Zealand presents all the characteristics of, and is properly treated as a distinct province for the purposes of a description and classification of its animal and vegetable life (for the remarks I have quoted in regard to its Flora apply also to its Fauna,) yet it must also be considered as forming a part only of a greatly larger area, within which the Fauna, and Flora exhibit such a degree of affinity, as can only be accounted for by the former existence of means of inter-communication, of which all visible traces are now lost. In this connection, for example, it is highly interesting to know that except one or two plants not found in New Zealand, the whole Flora of the Chatham Islands, four hundred miles to the eastward of Banks' Peninsula, is absolutely identical with that of these islands, although some of the forms (as for example, Lomaria discolor, a common fern in our forests) have been somewhat modified in outward appearance, a fact itself of great and striking significance in connection with the views of Mr. Darwin. The same remarks also apply to the Flora of Raoul or Sunday Island, a small island some six or seven hundred miles to the north-east of the northern part of New Zealand, with this increased difficulty in accounting for the general identity between the two Floras (except on the supposition of a former extension of the land of New Zealand, as to include the several islands referred to) that the prevalent winds and the ocean currents between this country and Raoul Island, would drive us to the conclusion, that the former had been colonized from the latter, a supposition opposed to all our present knowledge in regard to the origin and distribution of life.

page 322

I will now proceed to offer a few remarks upon the distribution, in its leading characteristics, of the flora and fauna of these islands, which, however, I must do with great briefness, in order not to weary you. But first, let me repeat a remark made in my former lecture, as to the peculiar physical character of the surface of these islands, namely, that they present all the appearance of rugged mountain chains, which originally formed part of an immensely larger area, the greater part of the lower and more level tracts of which have since been submerged. Looked at broadly, in connection with the Flora, and exclusive of alpine and sub-alpine tracts, we may treat the surface of the Islands generally as divisible into bush or forest land, fern land, grass land, and swamp land. I apply the words "swamp land," in the local sense the term, to tracts usually found near the coasts, and covered with a rich growth of Phormium tenax, and other plants requiring a considerable depth of vegetable soil and much moisture, and by no means in the sense in which the same words would be used in England. Our swampy lands are easily drained and become very fertile under cultivation, and then yield, in this mild climate, immense and continuous crops of grass. Such tracts generally indicate the site of former forest growth, for, in every instance that I am aware of at a moderate depth below the surface, large quantities of timber are found. The area occupied by land of this class is not extensive, but it possesses considerable importance in an economical point of view, not merely on account of the fertility of the land itself, but also as yielding a large supply of one of the most valuable fibre plants in the world.

The grass lands occur chiefly, if not exclusively, on the eastern sides of both islands, and now afford pasture to millions of sheep and to great numbers of cattle and horses, thus, in their mere natural condition, adding largely to the wealth of the colony.

Whether these pasture lands were ever covered with forest I very much doubt, although many great naturalists are of opinion, that every part of the surface of the habitable earth, in all climates and regions, was covered with forest growth before it first became the home of man. Nor is enquiry into this question material to the subject under consideration, for it is clear that little, if anything, had been done before these Islands became the abode of civilized man to alter or modify the character or distribution of its vegetation. I have never travelled over the pastoral tracts of the North Island, and am therefore unable to point out what general differences exist (if any do exist) between the grasses there, and those which cover the pastoral lands of the Middle Island. The latter until used as sheep and cactle runs, consisted chiefly of tussock grasses, growing with more or less luxuriance according to the nature of the soil, but presenting only slight differences in character, in their [unclear: atitudinal] range.

When these Islands were first colonized by us, very large tracts were covered with Fern, chiefly "Pteris aquilina." I have little doubt that the greater part of such lands had originally been occupied by forest, destroyed by fire after the occupation of the country by the present native inhabitants. The soil occupied by this growth is usually friable and easily worked, and wherever the fern grew luxuriantly, has turned out valuable for agricultural purposes. The "Bush" or Forest may be roughly divided into three classes, namely, 1st, That which occupies the lower parts of our larger valleys and other low lying tracts near the sea coast,—2nd, That which occupies the upper or higher parts of our valleys, and hills of moderate elevation, within a few miles from the coast line,—and 3rd, That which occupies the greater mass of the mountain districts on the western sides of both islands, up to sub-alpine elevations.

The first class comprises a varied growth, the timber trees belonging, for the most part to certain peculiar genera of Coniferæ, whilst the undergrowth page 323 is usually very luxuriant and dense, more particularly in the deep alluvial deposits at the lower parts of the valleys, where we also find the Laurelia Novæ Zelandiæ and other trees affecting rich moist soils. The small remnant of forest still seen at the entrance of the Hutt valley affords us an example of this class of bush land, and although it is fast being destroyed, it even now gives us an excellent idea of its original variety and density of growth. We still find there living specimens of most of the forest trees, covered with remarkable epiphytes, whilst amongst the undergrowth, the Tree Fern, the Nikau Palm, the Cordyline, and the Freycinetia, and a variety of shrubs delighting in shade and moisture, are closely interlaced with the Supple-jack, the Clematis, and other creeping plants. The second class also comprises a varied growth, but here we find, in addition to forms of Coniferæ occurring in the lower grounds, many species of Metrosideros, Elæocarpus and other timber trees, whilst the undergrowth is also extremely dense and impenetrable, more particularly in the innumerable gullies which have been furrowed in every direction out of the hill sides. Those, however, who can be tempted to explore these dense gullies, are amply repaid for their toil by the extreme beauty and variety of the ferns and mosses with which the ground is carpeted, and the trunks of the trees are covered, whilst the appearance of many of the more gigantic forest trees, is rendered singularly beautiful, by the enormous mass of epiphytes with which they are covered. The third class consists almost exclusively of species of Fagus, with a very sparse undergrowth of Aralia, Coprosma, Rubus, etc. These enormous beech forests will, no doubt, become valuable as the country becomes more thickly peopled, for the timber is well adapted for shipbuilding, and for a large variety of other useful purposes, and the bark yields a considerable quantity of tannin. The great difference in appearance which these Beech forests present, as compared with the other classes of bush to which I have referred, is very striking. As a rule they are open and easily traversed, but the eye becomes fatigued, and the mind oppressed by their monotony, and by the general absence of life which characterises them.

To the North of the Isthmus between Auckland and the head of the Manukau occur extensive forests of kauri, the only true coniferous tree found in these Islands. It does not now occur as a common tree south of the above line, though I am informed that single specimens have been observed as far south as Kawhia; but the bituminous shales associated with some of the coals of Otago, present numerous impressions of forms of Dammara closely allied to the living tree, leading us to the conclusion that the latter is the modified descendant and representative of forms which flourished abundantly during those far distant periods. A fossil [unclear: guns], chemically undistinguishable from the kauri gum of the north, is also found in the brown coals throughout these Islands, and even in the Chatham Islands, from which we may also infer that these coals are in part derived from altered wood of trees belonging to the same germs, which formed part of the earlier vegetation of that larger area, of which New Zealand is assumed to be only a remnant.

With the Fauna of these Islands I must deal even more sketchily than I have done with the Flora, for, with the exception of its birds, very little has been attempted towards illustrating this branch of their Natural History. The only mammal (exclusive of two or three species of Bat) which was known to be indigenous to these Islands, was the Kiore, or so-called Native rat. It has been the fashion to assume that before the arrival of Europeans in this Colony, this creature was common, and to attribute its destruction to the European [unclear: ant] and, indeed, the natives have been credited with a proverb in relation to this point It is not in effect impossible, that the ultimate destruction of those which still existed when trade was first opened between Europeans and the Natives, long after the colonization of New South Wales, may have been page 324 hastened by the introduction of the European rat; but I am satisfied that before that time they had become very scarce, and indeed I have been told by gentlemen who have lived in the northern part of this Island for upwards of forty years, that they never saw a specimen.

The Birds of New Zealand have been collected and investigated by Ma Walter Buller, who has long promised a more extensive work on the subject, than the pamphlet published in the first volume of our Transactions.

The number of species of land birds is not large in itself, though, as Mr. Buller remarks, the ornithology of these islands does not compare unfavourably in this respect with that of temporate conntries in the Northern hemisphere, but although in regard to number of species it may not be important, our birds present many peculiarities interesting to zoologists.

We have, for example, the wingless Apteryx (or Kiwi), the present representative of gigantic races of birds which formerly roamed over our plains and open lands; the Kakapo, or Ground Parrot, inhabiting excavations in the ground, and strictly nocturnal in its habits. Both of these species are confined to our forest-clad ranges, and the latter has not, so far as I am aware, been found in the North Island. We have also, though now very rare, the beautiful Notornis Mantelli, a large Rail, the plumage of which is extremely rich and varied in colour. This bird is known to exist in both islands, but whether the species is in each case strictly identical, I am unable to say. Species of the Wood hen (Ocydromus) are found in both islands, and this bird is abundant, if not actually increasing in the Middle Island.

Amongst the other land birds more familiar to us are the Kaka or Nestor meridionalis, the Pigeon, the Tui or Parson bird; and several species small perching birds found in every wood. Many of the New Zealand perching birds are honey-feeder's, and, the great majority are insect-feeders. The Kaka feeds largely upon the honey of the phormium tenax, and upon the flowers of the rata. Of ducks there are several species, for example, the Paradise duck (more properly speaking a goose), the Grey duck, the Blue or Mountain duck, and some varieties of Teal. The Paradise duck is a remarkably handsome bird, the female differing completely from the male plumage.

Of wading birds we have many, amongst others, a magnificent white Crane (Ardea flavirostris), a handsome blue Crane (Ardea matuku), a Bitters (Botaurus poicilopterus), the Pukeko (Porphyrio melanotus), and several smaller birds. The Crane and Bittern are scarce, but the Pukeko is to be found in large numbers in every swamp, and more particularly in those which about upon cultivations. This bird is indeed more inclined by appetite to cereal grains and plants than to aquatic herbs, and frequents the land more than it does the water. It is handsome and graceful, and active in its movements. It is easily tamed, and mingles readily with ordinary domestic poultry. As these birds are also found in the eastern and southern provinces of Europe, we may accept their presence in this Colony as some indication of the adaptability of our climate to animals, birds, and plants indigenous to mild latitudes.

Of the poultry tribe, except the Pigeon referred to before, I only know the Quail, a delicious eating bird, which, unfortunately, is rapidly disappearing but which formerly existed on the plains and in all the river valleys in considerable numbers. It has indeed been said that as many as forty brace and upwards sometimes fell to a pair of guns in a single day's shooting.

Of rapacious birds we have several species. A small Hawk, distinguished like its European congener for its daring; a large Kite, and two or three species of Owls. These birds kill vast numbers of rats and mice, and thus more than compensate for the loss of a few chickens and ducklings. I was once told by a German settler that his young chickens, etc., were never page 325 molested by these birds, (although they existed in great numbers in his neighborhood), when under the charge of a turkey mother.

From noxious reptiles this country is happily free, and we shall scarcely require to import boa constrictors from St. Lucia (as recommended by Sir Charles Darling, to the Acclimatization Society of Victoria), for the purpose of devouring them.

With the indigenous sea fish, and the marine crustacea and testacea we are but little acquainted. The Hapuka, Baracouta, Ling, Snapper, Kawai, and Moki, a species of Flounder, and a few varieties of Rock fish, are the sea fish chiefly obtained and used, and of most of these, as indeed of a large number of the New Zealand sea fish, it may be said, that they are poor in flavour and coarse in flesh, affording a most striking contrast in this respect to the many delicious species found in English waters. There are two species of salt-water Crayfish, both coarse; some excellent Oysters, and a few of the commoner shell fish, such as Mussels, Cockles, Limpets, etc.; but until lately nothing has been done to extend the knowledge obtained by the very earliest colonists in respect to our marine fauna.

Of fresh water fish, we have Eels of several kinds, all extremely good eating; Lampreys, said by the natives to be delicious, and the fry of a fish as yet unascertained, which ascends the rivers in the months of October and November, and is used as whitebait

In the Province of Nelson, during the month of April, shoals of a small fish from a quarter to half a pound in weight, and of delicious flavour, ascend be rivers, and are then eagerly sought for by epicures, but I am not aware that any attempt has been made to ascertain the ordinary habits of this fish.

Of the invertebrata, we have great numbers, but no great variety, in species of the spider. Moths, and consequently their larvæ, are extremely numerous, and the latter, as well as the larva; of certain species of beetles, frequently do great damage to the grain and other crops.

There are several varieties of indigenous flesh, and other flies, which are found to be great pests, and they, as well as the imported house and cattle flies, are increasing to an extent which threatens to prove a serious source of damage and discomfort. My own opportunities of observation have been too limited to enable me to point out the checks now in operation to the further and more destructive increase of these insects, but I am convinced that it is of great importance that we should speedily add to the number of those checks, unless we are willing to submit to severe injury and loss. It has been said by a great author, in reference to the injuries which insects can do us, "that the Almighty ordains various instruments for the punishment of offending nations; sometimes he breaks them to pieces with the iron rod of war; at others the elements are let loose against them; earthquakes and floods of fire at his word being sudden destruction upon them; seasons unfriendly to vegetation threaten them with famine; the blight and mildew realize these threats; and often, the more to manifest and glorify his power, he employs means, at first sight, apparently the most insignificant and inadequate, to effect their ruin; the numerous tribes of insects are his armies, marshalled by him, and by his irresistible commands impelled to the work of destruction; where he directs them, they lay waste the earth, and famine and the pestilence often follow in their train.

"The generality of mankind overlook or disregard these powerful, because minute, dispensers of punishment; seldom considering in how many ways their welfare is affected by them, but the fact is certain, that should it please God to give them a general commission against us, and should he excite them to attack, at the same time, our bodies, our clothing, our houses, our cattle, and the produce of our fields and gardens, we should soon be reduced, in every possible respect, page 326 to a state of extreme wretchedness, the prey of the most filthy and disgusting diseases, divested of a covering, unsheltered, except by caves and dungeons from the inclemency of the seasons, exposed to all the extremities of want and famine;" and in the end, as Sir Joseph Banks, speaking on this subject, has well observed, "driven with all the larger animals from the face of the earth." You may smile, perhaps, and think this a highly coloured picture, but you will recollect, I am not stating the mischiefs that insects commonly do, but what they would do, according to all probability, if certain counter checks, restraining them within due limits had not been put in action; and which they actually do, as you will see, in particular cases, when those counter-checks are diminished or removed.

It might, indeed, be supposed, that the injuries which can be inflicted upon man by insects have often been exaggerated, but our own experience during the last few years completely justifies these ideas. You may, for example, remember the nearly total annihilation of the cabbage, cauliflower, turnip, and other vegetables belonging to the large cruciferæ in the year 1862, caused by an aphis which had not previously appeared in this country. Our apple trees are the prey of another insect of the same kind—the aphis lanifera—commonly called the American blight, which has put a stop to the cultivation of orchards on a large scale. The rapidity with which these creatures increase is something marvellous, though less so when we find that the ordinary laws of generations are suspended in regard to them, the production of young without fecundation being common to the whole family. Bounet long ago demonstrated, by a series of most carefully conducted experiments, that at least five generations of the aphis sambuci may succeed each other, the females never pairing. The oak aphis carried this to the ninth generation, and, strange to state, he found that whilst, after pairing, the aphides produced ova, in other cases they produced their young alive. Reaumur computes that each aphis may produce about ninety young, and that in consequence, in five generations the descendants from a single insect would amount to the astonishing number of 5,904,900,000. "Were it not," says Mr. Swainson, "that these immense multitudes are called into being to furnish food for other races, they would be sufficient to destroy vegetation and annihilate the empire of Flora."

Having thus (I am afraid, however, in a very off-hand manner) pointed out to you the leading characteristics and distribution of the Flora and Fauna of these islands, I will now call your attention to what has aptly been termed the "Struggle for Existence" which living organisms of all kinds, are exposed to in a state of nature, and point out in what manner variation lends its aid in protecting both animals and plants from extinction under that struggle, In doing this I shall not hesitate to borrow largely from Mr. Darwin's work. After adverting to the acknowledged variability of organic beings in a states nature (to which I have called your attention in an earlier part of this lecture) he asks, "How all those exquisite adaptations of one part of the organization to another part, and to the conditions of life, and of one distinct organic being to another, have been perfected? How it is that varieties, (which by the war he has called 'incipient species'), became ultimately converted into good and distinct species, which, in most cases, obviously differ from each other far more than do the varieties of the same species? How those groups of species which constitute what are called distinct genera, and which differ from each other more than do the species of the same genus, have arisen?" And he proceeds to answer these questions by saying, that the results referred to all follow from the "Struggle for Life," in which all the members of the organic world are engaged. Owing to this struggle," he observes, "any variation, however slight, and from whatever cause proceeding, if it be in any degree profitable to a individual of any species, in its infinitely complex relations to other organic page 327 beings and to external nature, will tend to the preservation of that individual, and will generally be inherited by its offspring. The offspring, also, will thus have a better chance of surviving, for, of the many individuals of any species which are periodically born, but a small number can survive.

"This struggle for existence inevitably follows from the high rate at which all organic beings tend to increase. Every being which during its natural lifetime produces several eggs or seeds, must suffer destruction during some period of its life, and during some season or occasional year, otherwise, on the principle of geometrical increase, its numbers would quickly become so inordinately great, that no country could support the product. Hence, as more individuals are produced than can possibly survive, there must in every case be a struggle for existence, either one individual with another of the same species, or with Individuals of distinct species, or with the physical conditions of life. It is the doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms; for in this case there can be no artificial increase of food, and no prudential restraint from marriage. Although some species may be now increasing, more or less rapidly, in numbers, all cannot do so, for the world would not hold them.

"There is no exception to the rule that every organic being naturally increases at so high a rate, that if not destroyed, the earth would soon be covered by the progeny of a single pair. Even slow breeding man has doubled in twenty-five years, and at this rate in a few thousand years there would literally not be standing room for his progeny. Linnæus has calculated that if an annual plant produced only two seeds—and there is no plant so unproductive as this—and their seedlings next year produced two, and so on, then in twenty years there would be a million plants. The elephant is reckoned the slowest breeder of all known animals, and I have taken some pains to estimate its probable minimum rate of natural increase; it will be under the mark to assume that it breeds when thirty years old, and goes on breeding till ninety years old, bringing forth three pair of young in this interval; if this be so, at the end of the fifth century there would be alive fifteen millions of elephants, descended from the first pair.

"But we have better evidence on this subject than mere theoretical calculations, namely, the numerous recorded cases of the astonishingly rapid increase of various animals in a state of nature, when circumstances have been favourable to them during two or three following seasons. Still more striking to the evidence from our domestic animals of many kinds which have run wild in several parts of the world; if the statements of the rate of increase of slow breeding cattle and horses in South America, and latterly in Australia, had not been well authenticated, they would have been incredible. So it is with plants: cases could be given of introduced plants which have become common throughout whole islands in a period of less than ten years. Several of the plants, such as the cardoon and a tall thistle, now most numerous over the wide plains of La Plata, clothing square leagues of surface almost to the exclusion of all other plants, have been introduced from Europe; and there are plants which now range in India, as I hear from Dr. Falconer, from Cape Comorin to the Himalaya, which have been imported from America since its discovery. In such cases, and endless instances could be given, no one supposes that the fertility of these animals or plants has been suddenly and temporarily increased in any sensible degree. The obvious explanation is that the conditions of life have been very favourable, and there has consequently been less destruction of the old and young, and that nearly all the young have been enabled to breed. In such cases the geometrical ratio of increase, the result of which never fails to be surprising, simply explains the extraordinarily rapid increase and wide diffusion of naturalized productions in their new homes.

page 328

"In a state of nature almost every plant produces seed, and amongst animals there are very few which do not annually pair. Hence we may confidently assert, that all plants and animals are tending to increase in a geometrical ratio, that all would most rapidly stock every station in which they could any how exist, and that the geometrical tendency to increase must be checked by destruction at some period of life. Our familiarity with the larger domestic animals tends, I think, to mislead us; we see no great destructions falling on them, and we forget that thousands are annually slaughtered for food, and that in a state of nature an equal number would have somehow to be disposed of.

"The only difference between organisms which annually produce eggs or seeds by the thousand, and those which produce extremely few, is, that the slow breeders would require a few more years to people, under favourable conditions, a whole district, let it be ever so large. The condor lays a couple of eggs, and the ostrich a score, and yet in the same country the condor may be the more numerous of the two : the Fulmar petrel lays but one egg, yet it is believed to be the most numerous bird in the world. One fly deposits hundreds of eggs, and another, like the hippobosca, a single one; but thus difference does not determine how many individuals of the two species can be supported in a district. A large number of eggs is of some importance to those species which depends on a rapidly fluctuating amount of food, for it allows them rapidly to increase in number. But the real importance of a large number of eggs or I seeds is to make up for much destruction at some period of life; and this period in the great majority of cases is an early one. If an animal can in any way protect its own eggs or young, a small number may be produced, and yet the average stock be fully kept up; but if many eggs or young are destroyed, many must be produced, or the species will become extinct. It would suffice to keep up fully the numbers of a tree, which lived on an average for a thousand years, if a single seed were produced once in a thousand years, supposing that this seed were never destroyed, and could be ensured to germinate in a in fitting place. So that in all cases, the average number of any animal or plant depends only indirectly on the number of its eggs or seeds."

The author then proceeds to comment upon the causes which check the natural tendency of each species to increase in number, and points out not only the extreme obscurity of these causes, but also that even when at all ascertain able, they are found to be very complex and unexpected. Of this he gives several striking instances, as, for example :—

"In Staffordshire, on the estate of a relation, where I had ample means of investigation, there was a large and extremely barren heath, which had never been touched by the hand of man; but several hundred acres of exactly the same nature had been enclosed twenty-five years previously, and planted with Scotch fir. The change in the native vegetation of the planted part the heath was most remarkable, more than is generally seen in passing from one quite different soil to another; not only the proportional numbers of the heath plants were wholly changed, but twelve species of plants (not counting grasses and carices) flourished in the plantations, which could not be found on the heath. The effects on the insects must have been still greater, for six insectiverous birds were very common in the plantations, which could not be found on the heath; and the heath was frequented by two or three distinct insectiverous birds. Here we see how potent has been the effect of the introduction of a single tree, nothing whatever else having been done, with the exception that the land had been enclosed, so that cattle could not enter. But how important an element enclosure is, I plainly saw near Farnham, in Surrey Here there are extensive heaths, with a few clumps of old Scotch firs on the distant hill-tops : within the last ten years large spaces have been enclosed, page 329 and self-sown firs are now springing up in multitudes, so close together that all cannot live. When I ascertained that these young trees had not been sown or planted, I was so much surprised at their numbers that I went to several points of view, whence I could examine hundreds of acres of the unenclosed [unclear: heath], and literally I could not see a single Scotch fir, except the old planted dumps. But on looking closely between the stems of the heath, I found a [unclear: altitude] of seedlings and little trees, which had been perpetually browsed down by cattle. In one square yard, at a point some hundred yards distant from one of the old clumps, I counted thirty-two little trees; and one of them, with twenty-six rings of growth, had during many years tried to raise its head, and had failed. No wonder that, as soon as the land was enclosed, it became thickly clothed with vigorously growing young firs. Yet the heath was so extremely barren and so extensive, that no one would ever have imagined that cattle would have so closely and effectually searched it for food.

"Here we see that cattle absolutely determined the existence of the Scotch fir in this particular locality and under the conditions indicated; but in several parts of the world insects determine the existence of cattle. Perhaps Paraguay offers the most curious instance of this; for here neither horses, nor cattle, nor dogs, have ever run wild, though they swarm northward and southward in a feral state; and Azara and Rengger have shown that this is caused by the great number in Paraguay of a certain fly, which lays its eggs in the navels of these animals when first born. The increase of these flies, numerous as they are, must be habitually checked by some means, probably by birds. Hence, if certain insectivorous birds (whose numbers are probably regulated by hawks or beasts of prey) were to increase in Paraguay, the flies would decrease—then cattle and horses would become feral, and this would certainly greatly alter (as indeed I have observed in parts of South America) vegetation; this again would largely affect the insects; and this, as we have just seen in Staffordshire, the insectivorous birds, and so onwards in ever increasing circles of complexity. We began this series by insectivorous birds, and we have ended with them. Not that in nature the relations can ever be as simple as this. Battle within battle must ever be recurring with varying success; and yet in the long run the forces are so nicely balanced, that the face of nature remains uniform for long periods of time, though assuredly the merest trifle would often give the victory to one organic being over another, nevertheless so profound is our ignorance, and so high our presumption, that we marvel when we hear of the extinction of an organic being; and as we do hot see the cause, we invoke cataclysms to desolate the world, or invent laws on the duration of the forms of life!"

The same author further adds :—

"I am tempted to give one more instance showing how plants and animals, most remote in the scale of nature, are bound together by a web of complex nations. I shall hereafter have occasion to show that the exotic Lobelia fulgens, in this part of England, is never visited by insects, and consequently, from its peculiar structure, never can set a seed. Many of our orchidaceous plants absolutely require the visit of moths to remove their pollen-masses, and thus to fertilize them. I have, also, reason to believe that humble-bees are indispensable to the fertilization of the heartsease (Viola tricolor), for other bees do not visit this flower. From experiments which I have lately tried, I have found that the visits of bees are necessary for the fertilization of some kinds of clover; but humble-bees alone visit the red clover (Trifolium pratense), as other bees cannot reach the nectar. Hence I have very little doubt, that if the whole genus of humble-bees became extinct or very rare in England, the heartsease and red clover would become very rare, or wholly disappear. The number of humble-bees in any district depends in a great degree on the number of field mice, which destroy their combs and nests; and Mr. H. Newman, who has page 330 long attended to the habits of humble-bees, believes that 'move than two-thirds of them are thus destroyed all over England.' Now the number of mice is largely dependent, as every one knows, on the number of cats; and Mr, Newman says, 'Near villages and small towns I have found the nests of humble-bees more numerous than elsewhere, which I attribute to the number of cats that destroy the mice.' Hence it is quite credible that the presence of a feline animal in large numbers in a district might determine, through the intervention first of mice, and then of bees, the frequency of certain flowers in that district!"

In summing up the results of his enquiries, Mr. Darwin has applied the term "Natural selection" to the principle or operative agency, which the foregoing extracts are intended to illustrate, viz., that principle under which slight variations in any species tend, if useful, to be accumulated and to be preserved to succeeding generations. The term "Natural selection" was adopted by Mr. Darwin in order to mark the relation of the principle or agency in question, to the power which man exercises over domestic animals, for, as you are aware, man by taking advantage of variations in character amongst domesticated animals has been able to produce a large number of breeds and varieties, more or less useful to himself. It must not, however, be supposed that nature operates as rapidly or necessarily in the same direction as man in assimilating such variations.

"Man," says Mr. Darwin in his work on "Animals and Plants under Domestication," "selects varying individuals, sows their seeds, and again selects their varying offspring. He may be said to be trying an experiment on a gigantic scale, but the initial variation on which he works, and without which he can do nothing, is caused by slight changes in the conditions of life which must often have occurred under nature. The experiment which man has been making is one which nature, during the long lapse of time, has incessantly tried."

To sum up again: I have now briefly shown you—by reviewing the investigations of modern writers on such subjects, and chiefly those of Hooker, Lindley, Darwin, Lyell, and Marsh,—the divisions and subdivisions of the organic world; the laws which regulate the geographical distribution of plants and animals; the tendency to vary which characterises living organisms; the principles under which any variation, however slight and from whatever cause proceeding, if it be profitable, tends to the preservation of the individual; the transmissibility of acquired variations in character and the struggle for existence which all life is engaged in.

And I have also shortly called your attention to the distribution, affinitives, and general characteristics of the Flora and Fauna of these Islands—sketchily it is true—but sufficiently for the purposes of my further observations, if. As I have a right to suppose, you have made any reasonable use of the opportunities you enjoy in common with myself, of acquiring more detailed knowledge regard to them.

It was my intention originally to have dealt with the whole of my subject in this lecture, but I have found it impossible to do so, and I am compelled to defer to a future occasion a consideration of the position, (relatively to the questions discussed in this and in my last lecture), in which our Flora and Fauna stood immediately before the systematic colonization of these islands, and the effects already produced, and likely to follow, from the introduction of competing foreign organisms. This, of course, I can only do broadly and briefly, but I hope to satisfy you, that the operations now going on are calculated to produce all the results which I have suggested as probable in the future