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The Atoll of Funafuti, Ellice group : its zoology, botany, ethnology and general structure based on collections made by Charles Hedley of the Australian Museum, Sydney, N.S.W.

Order Siphonophora. — Family Physalidæ. — Physalia megalista, Lamk

Order Siphonophora.
Family Physalidæ.
Physalia megalista, Lamk.

Physalia megalista, Lamk., Anim. sans Vert., ii,, 1816, p. 481; Peron et Lesueur, Voy. de Déscouvertes aux terres australes, Atlas, 1807, pl. xx., fig. 1; Haeckel, Chall. Rep. Zool., xviii., pp. 351-372.

Numerous examples of this species were obtained by Mr. Hedley, who also made a coloured sketch from a living specimen; the colours exhibited in the drawing, and by the specimens when received, agree with examples of this species from the coast of New South Wales.

During the past five or six years I have paid special attention to the Physalidæ occurring on our coast; two species have been observed, i.e., Physalia megalista and P. utriculus.* They occur nearly all the year round with favourable winds, such as N.E., E., or S.E., occasionally in company, but more frequently only one species is obtainable at a time. I have at various times closely examined hundreds of living individuals of both species, and can readily separate the two by their colour alone. There are, however, other more important characters which clearly indicate that they are specifically distinct.

In Physalia megalista the crest is long in proportion to the rest of the pneumatophore, whilst the anterior crestless portion is remarkably short. The ventral group of cormidia are arranged in well defined clusters, two anterior and three posterior to the main tentacle. Each cormidium consists of a short broad pedicel—more or less transverse to the axis—and a series of short branchlets from which arise the ventral appendages: siphons, tentacles, pal-pons, and gonodendria.

The basal group of cormidia are separated from the ventral by a very short space. They consist of five or six clusters of small palpons, siphons, and frequently from one to three tentacles in addition to that which subtends the terminal proto-siphon.

* Chun unites all the Pacific and Indian Ocean forms under the name of Physalia utriculus. (See Zool. Anzieg., x., 1887, p. 558.)

page 378

The presence of accessory tentacles in the basal group of cor-midia, appears to have hitherto been overlooked in the genus Physalia.

Prof. E. Haeckel, in the " Challenger " Report,* remarks that "The smaller basal group, at the posterior or distal end of the trunk, produces merely a series of small siphons and palpons, placed before the protosiphon and is provided with a single tentacle only it always remains sterile and never produces gono-phores." And again, on page 344: "The primary tentacle which belongs to the protosiphon, remains either as the single tentacle of the basal cormidium, or it is afterwards lost; but I have never seen secondary tentacles developed in this distal group."

From the above remarks it seems clear that the secondary tentacles occurring in the basal group of cormidia have escaped notice. This may be due to imperfect or ill-preserved specimens from which some of the species have been described.

In living or well-preserved examples of either Physalia utriculus or P. megalista, the basal tentacles are very conspicuous and may be easily seen by the unaided eye. In badly preserved specimens, in which the tentacles are generally more or less contracted, they are not so evident; they can, however, be readily distinguished with a hand lens of moderate power.

With a view of rendering it less difficult to separate the two Pacific species, I have carefully dissected and measured a series of specimens of each. The results are embodied in the accompanying tables.

In dissecting the specimens, I began by isolating the anterior cormidia, and afterwards snipping off the entire bunch of appendages without rupturing the pneumatophore. The siphons, tentacles, and gonodendria were then separated and counted. The palpons have not been taken into account.

In the first twelve enumerated in the table, the siphons of the basal groups have not been noted. In the last six, the whole of the cormidial appendages—palpons excepted—both ventral and basal have been enumerated. The gonodendria were counted according to age; thus, in some cases, as many as four occur in one cormidia, all being in a different state of development. In the larger examples of P. utriculus, it often proved difficult to determine whether the last (sixth) ventral cormidium should he regarded as one cluster or two; frequently there is a clear space on each side, indicating two pedicels, but the dividing line is not continued through the centre.

* Haeckel—"Challenger" Report—Zoo], xviii., p. 311.

page 379
P. Megalista (From Funafuti).
Ventral cormidia Basal cormidia. Total Ventral cormidia Total Basal cormidia
1st 2nd 3rd 4th 5th 6th 1st 2nd 3rd 4th 5th 6th
Length of specimen, 25 mm. 25 mm
Number of siphons 8 7 5 7 9 36
Number of tentacles 3 3 1 3 3 3 1 1 16 2
Number of gonodendria 1 1 1 1 4
Length of specimen, 30 mm. 30 mm
Number of siphons 14 12 12 10 18 66
Number of tentacles 5 3 1 5 4 3 0 1 21 1
Number of gonodendria 1 1 1 3
Length of specimen, 35 mm. 35 mm
Number of siphons 8 6 3 8 10 35
Number of tentacles 3 1 1 1 4 3 1 1 13 2
Number of gonodendria 1 1 1 3
Length of specimen, 40 mm. 40 mm
Number of siphons 10 10 8 8 14 50
Number of tentacles 4 3 1 3 1 4 0 1 16 1
Number of gonodendria 1 1 1 3
Length of specimen, 55 mm. 55 mm
Number of siphons 17 19 14 12 16 78
Number of tentacles 5 7 1 5 5 6 3 1 29 4
Number of gonodendria 1 1 2
P. Megalista (From Makoubra, New South Wales).
Length of specimen, 45 mm. 45 mm
Number of siphons 11 7 10 9 12 47
Number of tentacles 3 4 1 5 5 3 1 1 21 2
Number of gonodendria 1 1 1 1 4
Length of specimen, 50 mm. 50 mm
Number of siphons 15 9 12 14 17 67
Number of tentacles 5 7 1 5 6 5 3 1 29 4
Number of gonodendria 3 2 2 1 1 9 page 380
Length of specimen, 60 mm. 60 mm
Number of siphons 12 12 12 10 25 71
Number of tentacles 5 8 1 5 5 5 2 1 29 3
Number of gonodendria 1 1 1 2 1 6
Length of specimen, 65 mm. 65 mm
Number of siphons 18 12 12 10 12 64
Number of tentacles 7 8 1 8 6 4 2 1 34 3
Number of gonodendria 1 2 1 1 1 6
Length of specimen, 70 mm. 70 mm
Number of siphons 15 12 16 12 20 75
Number of tentacles 7 9 1 7 7 7 0 1 38 1
Number of gonodendria 1 1 2 1 3 8
P. Megalista (From Makoubra, New South Wales).
Length of specimen, 50 mm. 50 mm
Number of siphons 20 22 26 28 40 4 2 1 0 0 1 136 8
Number of tentacles 6 5 1 6 5 10 3 3 1 0 0 1 38 8
Number of gonodendria 2 2 3 3 1 11
Length of specimen, 50 mm. 50 mm
Number of siphons 18 21 25 34 54 4 2 1 0 0 1 152 10
Number of tentacles 7 7 1 5 8 14 3 2 2 2 0 1 42 10
Number of gonodendria 2 2 2 1 2 9
Length of specimen, 55 mm. 55 mm
Number of siphons 26 34 30 34 40 5 2 1 0 0 1 164 9
Number of tentacles 7 5 1 5 6 8 3 2 0 0 0 1 32 6
Number of gonodendria 1 3 2 1 7
Length of specimen, 60 mm. 60 mm
Number of siphons 24 28 23 32 40 5 3 1 0 0 1 147 10
Number of tentacles 7 10 1 6 6 13 3 2 1 0 0 1 43 7
Number of gonodendria 1 2 2 2 7
Length of specimen, 70 mm. 70 mm
Number of siphons 26 28 28 24 48 4 3 2 0 0 1 154 10
Number of tentacles 7 7 1 8 7 10 4 3 2 0 0 1 40 9
Number of gonodendria 1 2 2 2 1 8
Length of specimen, 120 mm. 120 mm
Number of siphons 54 50 60 51 87 19 10 12 5 0 1 302 47
Number of tentacles 15 14 1 15 10 27 7 5 5 4 0 1 82 22
Number of gonodendria 4 3 4 3 6 20
page 381

The foregoing table, although not exhaustive, exhibits a wide difference between the two species, especially in the number of ventral siphons and the secondary tentacles of the basal cor-midia.

In Physalia megalista the lowest number of siphons is 35, the highest 78; in P. utriculus the lowest is 136, the highest 302, or, leaving out the large specimen, 164. The secondary basal tentacles in the former vary from 1 to 4, and in the latter from 6 to 22.

There are other important characters, which exhibit a number of differences in the length, colour, or distance of one part from another; some of these, although varying slightly in themselves within certain limits, are pretty constant in each species, and are very evident when the two species are compared. They may be enumerated as follows:—

P. megalista.
Crest of pneumatophore long
Apical crestless portion short
Distance between ventral and basal cormidia short
Length occupied by basal group of cormidia long
Apex of pneumatophore green
Summit of crest magenta
Mouths of siphons yellow
P. utriculus.
Crest of pneumatophore short
Apical crestless portion long
Distance between ventral and basal cormidia long
Length occupied by basal group of cormidia short
Apex of pneumatophore blue
Summit of crest Campanula blue
Mouths of siphons white

With a view of testing the pneumatophore to see if it would yield any reliable specific character, I have carefully measured a series of living, dead, and preserved specimens. I am well aware that the pneumatophore is a very variable structure; but, as in most other organisms, when at ease or in a restful condition, it has a certain definite form which may be regarded as the shape of the living object when in a healthy normal state. In the follow-ing measurements—as far as the material would allow—specimens have been selected that came nearest to what I regard as the natural shape of the pneumatophore.

page 382
P. megalista. From Maroubra. P. megalista. From Funafuti. P. utriculus. From living specimens. P. utriculus. Fresh dead specimens Large specimen preserved in formol.
Number of specimen 1 mm. 2 mm. 3 mm. 4 mm. 1 mm. 2 mm. 3 mm. 4 mm. 1 mm. 2 mm. 3 mm. 1 mm. 2 mm. 3 mm. 4 mm. 1 mm.
Length of specimen 35 45 45 50 39 40 45 49 35 50 60 36 45 60 95 120
Number of primary chambers in crest 5 5 6 7 6 6 7 7 6 7 7 6 6 7 7
Length of crest 27 32 30 46 23 24 37 41 22 30 40 20 26 32 60 80
Length of crest anterior crestless portion 7 10 11 15 8 8 8 10 11 14 20 15 16 25 41 49
Distance from anterior end of crest to main tentacle 23 30 22 35 22 23 27 35 19 26 37 22 23 28 47 61
Distance from anterior end of crest to proto-siphon 30 41 40 47 30 35 45 50 20 31 53 30 28 39 65 85
Distance from posterior end of crest to main tentacle 17 17 17 27 20 17 20 17 13 15 23 15 14 20 35 37
Distance from posterior end of crest to proto-siphon. 22 25 20 24 16 21 23 20 15 22 25 14 17 23 36 36
Distance from main tentacle to protosiphon 29 35 31 33 25 35 30 34 25 32 41 24 21 35 50 51
Distance between ventral and basal groups of cormidia 6 7 9 5 4 7 6 5 1·9 32 18 10 11 11 14 20
Length occupied by basal group of cormidia 16 17 19 15 9 19 16 15 12 16 22 10 10 11 17 15
page 383

In the above measurements, certain factors must be taken into consideration. In living specimens stranded on the beach, or examples kept for some time in confinement, the anterior crestless portion of the pneumatophore is usually shorter than in healthy floating individuals. In very sick, dead, or dried examples, it generally attains to its normal proportions.

The posterior and ventral lobes usually contract a little under any circumstances, and are often much shorter in dried or preserved specimens than in life.

With a little care it is possible to preserve the pneumatophore in its natural shape. Specimens that are uninjured, and floating on the sea, may be caught in a wide-mouthed bottle, or placed in a vessel with a small quantity of sea-water. After a short time they generally assume a restful or normal condition. A 10 per cent. solution of formol will fix them without any perceptible change taking place. When fixation is completed, sufficient sea-water should be added to reduce the mixture to about one or two per cent., in which fluid they may be kept for years without much loss of form or colour.

The pneumatophore may also be dried with little or no altera-tion. I have succeeded in drying many specimens that have retained their natural form. My method of proceedure is as fol-lows:—The specimen is floated into a wide-mouthed bottle; when it has assumed its normal condition, it is plunged into the hot dry sand on the beach; then, as quickly as possible, the pneuma-tophore is rubbed with dry sand until all the surface moisture is absorbed; the appendages are then removed, and the specimen left in the sun; when thoroughly dry it is placed in fresh water to extract the salt, and afterwards again dried and placed in an air-tight bottle. Specimens dried in this manner have retained their shape for several years and exhibit no signs of deterioration except in colour.