The Sexual Phases of Myzostoma. 
245 
The dorsal and ventral aspect of one of the specimens is repre- 
sented in PI. 11 Figs. 26 aud 27. The body is triangulär in outline, 
the lateral edges being reflected dorsally like the brini of a tricorn 
hai Of the three sides one is anterior and bears the dorsally reflected 
pharynx, while the two others are lateral. The edges of the three 
folds are furnished with the usuai 20 cirri. The ventral surface 
is embossed with a number of peculiar thickenings. There is a 
longitudinal series of four raised and flattened lines extending along 
the mid-ventral line (Fig. 27 2;). In one specimen the second and third 
of these four thickenings were confluent. v. Graff has given a good 
description of the 10 parapodia; each of which bears at its base a 
large heartshaped and more or less flattened thickeuing. The penes 
(peìù are unusually large and well-developed, They are reflected 
dorsally along the sides of the body as a pair of thickwalled and 
somewhat tapering tubes. The suckers, too, are excessively developed 
and project considerably beyond the surface of the body. AH of 
these structures, suckers, cordate thickenings, penes and linear median 
thickenings give the ventral surface of the animai a sculptured or 
chiseled appearance. 
Sections showed that ali of the specimens were in the functionally 
hermaphrodite phase with much reduced or evanescent male organs. 
The transverse section, of which Fig. 28 represents a little more 
than one half, passes through the middle of the body cutting on 
either side a penis (pen)^ the mid-ventral thickening and third pair of 
parapodia [pr). As in many other cysticolous species the great bulk 
of the body consists of parenchymatous tissue. The intestine and 
its branches [int and ^V^^f.r) are accompanied by rather narrow ventral 
and dorsal ramifications of the body-cavity (eoe). In these latter 
ramifications the ova are found, either mature and floating freely in 
the lumen or attached to the walls and in different stages of 
growth. 
The ovaries [ov] are readily found, owing to their great affiuity 
for stains, and may be regarded as representing a type intermediate 
between the ovaries of 31. cirriferum and glahrum. The thickening 
of peritoneal epithelium from which each of the ovaries originales is 
not depressed into the underlying parenchyma as in M. glabriim^ 
but projects into the lumen of the body-cavity as in cirriferum. At 
the same time the thickening is split into several irregulär lobes or 
masses like those seen in the ovaries of M. glahrum. The ovaries 
of M. platypus^ however, differ from those of ali other Myzostomes 
17* 
