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W. M. Wheeler 
hitherto described in lying ventral to the intestinal rami- 
fications (see the npper part ofFig. 28)i. The minute structure of 
the ovary is like that of other species. Oocytes and accessory cells^ 
are readily distinguished by their size and staining, though both of 
these elements are more miniite than their equivalents in the preced- 
ing species. 
In Fig. 28 a few testicular follicles (^ 5 ) are seen embedded in the 
parenchyma beneath the terminal coelomic ramifications in the 
upturned lateral portion of the body, and also in what probably 
represents the lumen of the penis. 
Since the specimens of M. platypus were all taken from the 
same Crinoid and were all in very nearly the same stage, I can of 
course make no definite Statements concerning the sexual phases 
through which this species may pass. Utilizing, however, the facts 
which I have collected from other species, I infer that the stage of 
M. platypus described above, must correspond to the late herma- 
phrodite stage of M. cirriferum and glahrum. Had the specimens 
been killed somewhat later in the year, I doubt not that they 
would have been found to be purely female, without any traces of 
testes. Perhaps at this time young specimens in the male phase 
would have been found in the cyst of the Actinometra, 
6. M. helli n. sp. 
Of this species, which I take great pleasure in dedicating to Prof. 
F. Jeffkey Bell, three specimens were studied. They were taken 
from hard calcareous galls at the bases of the arms of Pentacrinus 
alter nicirrus. Fach gall contained but a single Myzostome. The 
Crinoids were collected at Station 214 (south of the Philippines) by 
the Challenger Expedition. 
The three parasites were whitish in color and varied in length 
from 2.25 — 2.5 mm. Dorsal and ventral views of one of the specimens 
are shown in PI. 11 Figs. 31 and 32. The lateral edges of the body 
are reflected dorsally tili they nearly meet. A few imperfectly 
developed cirri are observable towards the anterior ends of the 
lateral edges near the protruding tip of the pharynx, and five pairs 
of small pointed parapodia are readily distinguished on the ventral 
aspect. I failed to find any traces of a penis or of suckers either 
1 This figure has been inverted by the lithographer. 
