The Sexual Phases of Myzostoma. 
249 
intestinal ramitìcatìons and are attached to the bases of the dorso- 
ventral septa, one on either side. Even under the low magnification 
with which the section was drawn, the cespitose arrangement of the 
oocytes and their accessory cells could be made out; under a higher 
magnification the ovarian nature of these structures was perfectìy 
manifest. 
I regard the specimen as presenting the female (hysterogynous) 
stage in the development of the reproductive organs subsequent to 
that observed in the three specimens of the closely allied M. belli. 
Further histological details could not be made out on account of the 
rather poor preservati on of the specimen. 
M. cryptopodium is allied to v. Graff's 3/. pp.ntacrini^ as will 
be seen by comparing my description and figures with v. Graff's 
description ('84 b, pag. 62—64) and figures (PI. 11 Figs. 12—14). In 
M. pentacrini the parapodia are not concealed in pockets but project 
from the surface, although their bases »lie in shallow cavities«. 
))Suckers are entirely absent« in v. Graff s species and the margin 
of the body when unrolled «is covered with short cirri (c v. Graff 
also says that »the ramification of the intestinal cocca was very dis- 
tinct; it is more abundant in this species than in any other« (cf. 
V. Graff's PI. 12 Fig. 11). M. cryptopodium on the other band 
has fewer terminal cocca than any species in which these organs 
bave been described. Moreover M. pentacrini »is like the above 
mentìoned species \_M. deformator] hermaphrodite, but differs from 
the typical free-living forms, in that the male generative opening 
and testes are only developed on one side, on the other there are 
only small rudiments of them, and the space generally occupied by 
these organs is filled with the highly- developed ovarian follicles«. 
The length of M, pentacrini is only 1.7 mm. 
The cyst formed by v. Graff's species is also very different 
from that of M. cryptopodium. The cyst of the latter species is large 
and globular like that of M. tenuispinum (vide v. Graff's PI. 13 
Fig. 14) and contains only a single Myzostome. M. pentacrini »does 
not produce real cysts upon the arms of its host, but only swellings 
which gradually disappear«. Two to three individuals may inhabit 
one cyst, but when this is the case they are separated from one 
another by partitions. 
