AND DEVELOPMENT OF M YEIOTHEL A . 
557 
The Gonosome. 
The gonosome of Myriothela (Plate 55) consists of blastostyles with their gonophores 
and of claspers. 
The blastostyles (fig. 2, a , a, a ) arise from the hydranth towards its proximal or attached 
extremity. They may be followed over a section occupying about one fifth of the entire 
length of the extended hydranth, and spring from this region on all sides without any 
very definite arrangement. They are very contractile, somewhat fusiform in shape 
when extended, but more clavate in various states of contraction. Towards their free 
extremities they carry several scattered tentacles resembling those of the hydranth, but 
much smaller ; and where the tentacles cease to be borne the gonophores ( b , b, b) com- 
mence, and continue with an irregular scattered disposition to within a short distance 
of the attached end of the blastostyle. 
The structure of the blastostyles resembles, in all essential points, that of the 
hydranth, with the exception of their being entirely deprived of a mouth. Their 
gastric cavity communicates with that of the hydranth which bears them ; the villi-like 
processes of the endoderm are extremely well developed, and the spherical cells, loaded 
with brown granules, which enter into the composition of these processes are very 
abundant (Plate 57. fig. 14, a). The muscular lamella is well developed, and the struc- 
ture of the tentacles is quite the same as in the hydranth, the rod-like tissue and 
pedunculated capsules being similar in both*. 
The claspers (Plate 55. fig. 2, c, c, c, and Plate 57. fig. 14, b, b), as already mentioned, 
are long tentacle-like organs of a cylindrical form, slightly enlarged towards their 
distal extremity, where they terminate in a sucker-like disk. They spring, like the 
blastostyles, from the body of the hydranth, and mostly in pairs from two points 
close to the base of a blastostyle. They have, however, no definite arrangement; 
many blastostyles have no claspers at their base, and solitary claspers occur, not only 
at the base of a blastostyle, but here and there at some distance from it on the body of 
the hydranth. 
The claspers are very contractile. Their structure differs considerably from that of 
the blastostyle. The endoderm (Plate 56. fig. 11, a) is composed of an external 
layer of closely applied large cells with clear contents, and an internal looser layer of 
small round cells filled with brown granules, this internal layer surrounding a very narrow 
axile cavity. There are no villi-like processes. The ectoderm, except in the terminal 
enlargement, essentially resembles that of the blastostyles and hydranth. The muscular 
* Before I had an opportunity of examining specimens of Myriothela, I regarded the appendages which 
carry the gonophores not as true members of a zooidal colony, and therefore not as proper blastostyles, but as 
mere peduncular organs like those which carry the gonophores in Tubularia (Gymnoblastic Hydroids, p. 383). 
In thus viewing them I differed from Mr. Hincxs, who looked upon them as true zooids, having a reproductive 
function, and forming with the hydranth from which they spring a compound colony (Hincxs, Brit. Hydroid 
Zoophytes, p. 76). I must now abandon my former view and declare my entire agreement with Mr. Hincxs 
as to the true zooidal significance of these bodies. 
4 E 
MDCCCLXX V. 
