The Sexual Phases of Myzostoma. 
255 
de longueur qui portait sur son dos un male de 0.7 mm. Cet individu 
femelle ne presentait encore aucune trace d’ovaires mais avait deja 
la forme caracteristique de Tadulte.« This Observation is valuable, 
because it indicates the size of the animal when it attains its peculiar 
adult sbape. The ovaries were undoubtedly present, but were over- 
looked by Proüho. The oocytes were probably migrating to their 
points of attachment in the ramifications of the »uterus« (body-cavity), 
but had not yet grown to a sufficient size to attract Peouho’s atten- 
tion. • The testes had probably completely disappeared. 
Stage 4. 2.75 — 3.5 mm long. Individuals of this length have 
the appearance of PI. 12 Figs. 41 and 42 and in turn bear indi- 
viduals which are in stages 1 and 2. Sections show that the testes 
have completely disappeared, so completely that I have found it 
impossible to discover in the parenchyma any traces of their former 
location. The intestine sends out on either side three thin main 
branches (not cut in the section figured) which terminate in small 
diverticula in the upturned lateral portions of the body. The in- 
testinal ramifications are accompanied and enveloped by corresponding 
ramifications of the coelom [coe) (»uterus«, body-cavity). 
The two ovaries {ov), though much more massive than in stage 2, 
still retain their primitive position and may still be separated by a 
median vertical septum as in the younger stage (Fig. 48). Their 
Position is in stroog contrast to that of the ovaries of M. helli and 
cryptopodium. The ramifications of the body-cavity contain many 
ova in all stages of growtb, the younger ones being attached to its 
peritoneal lining, the older ones floating freely in its lumen. In Myzo- 
stomes older than the one from which Fig. 44 was drawn, the mature 
ova fill the »uterus« and its six main branches. The cytoplasm of 
the mature ova has the same vesicular appearance as in M. helli. 
A considerably magnified ovary of one of the specimens in this stage 
is shown in Fig. 45. It is split up into irregulär lobes, but still shows 
distinctly the intermingled pale oocytes and deeply staining acces- 
sory cells. 
This fourth and last phase of M. pulvinar is purely female 
and corresponds to the final phases of M. cryptopodium.^ cirriferum 
and glahriim. Further comparison of M. pulvinar with these and 
other species will be undertaken in the general part of this paper. 
