On the Gonostyles of tivo Antarctic Siphonophora. 21 



Specimen C. measures 8| inches in length by 0*4 inch 

 in diameter, and is slightly narrower at one end. It differs 

 from A. and B. in the fact that several — as many as seven — 

 gonophorea occur on one stalk, which may also bear several 

 cnidospheres (Fig. IV.). The stalk bearing the gonophores 

 and stalked cnidospheres may be 7 mm. in length, with a 

 basal diameter of 0*7 mm. It seems to me likely that C. 

 belongs to a different species, but it may be that an unknown 

 Siphonophore colony has dimorphic sexual palpons. The 

 fact that the specimens were found floating freely, suggests 

 that the gonostyles of Siphonophora may sometimes be 

 set adrift, and may enjoy a brief period of independent 

 viability. 



The specimens have not been particularly studied histo- 

 logically, but a few points of interest may be noted. 



(a) The body-wall shows a wrinkled ectoderm of large 

 elongated covering cells, among which, on the gonophores 

 and stalked cnidospheres, there are numerous very distinct 

 elongated oval stinging-cells or cnidoblasts. 



(6) Beneath the ectoderm is a strongly-developed muscular 

 layer (Fig. IL, if.), about 01 mm. in thickness, often showiug 

 over a dozen fibrils side by side, and with a curious sugges- 

 tion of cross-striation. This muscular layer, in thinned 

 form, is continued up the stalks of the gonophores for some 

 distance. 



(c) Then follows a very definite transparent middle 

 lamella (Fig. IL, ml.), which is continued below the ectoderm 

 into the gonophores and stalked cnidospheres, and internally 

 along the triangular processes. A piece of it, isolated 

 without breakage, appeared to have a fibrillar structure. 

 The apparent striation of the muscular layer seems to be 

 due to an outward extension of processes from the middle 

 lamella, between which the fibrils are interwoven. 



(d) The endoderm consists of very large vacuolated cells. 

 Some of those next the middle lamella appear to have 

 muscular roots. 



(e) The internal isosceles-triangular processes usually narrow 

 into one layer of cells on each side of an inward continuation 

 of the middle lamella. In other cases the triangular pro- 



