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W. M. Wheeler 
represented in Fig. 46. The ventral surface is quite fiat, the dorsal 
convex, at least towards the margins. The section Fig. 47 does not 
quite pass through the middle of the body. At one side just above 
the intestine, which is only beginning to send out diverticula (w^.r), 
a small mass of cells [ov] represents the first visible anläge of one 
of the ovaries. I admit that my Interpretation of this organ may 
be open to some doubt, although the fact that it appears on one 
side of the body first is really no serious objection. 
In the other specimen, however, which, though older than the 
one just described, is nevertheless soraewhat shorter (0.8 mm), the 
conditions are too clear to admit of misinterpretation. The most 
valuable section through this specimen is represented in Fig. 48. 
The contour of the section should be noted and compared with the 
contour of Fig. 47: it shows the beginning of a depression in the 
mid-dorsal line and an incipient reflection of the lateral edges of the 
body. The testes {ts), which are relatively smaller and more compact 
than in the preceding stage (Fig. 46), are evidently on the way to 
disappearing. Over the intestine, which shows the first traces of an 
evagination on either side, the »uterus« is distinctly seen. It is double 
in this region, but in sections further towards the posterior end of 
the body the two cavities fuse to form a single unpaired lumen. 
The two cavities in the figure are nearly fiUed with a mass of cells 
{ov) which under a higher power (Fig. 49) leave no doubt, whatever, 
as to their ovarial nature. The oocytes (or oogonia) are largo and 
clear and stand out in streng contrast to the small deeply staining 
accessory cells which He between and among them. The general 
tufted, or cespitose arrangement of the cells is like that in the 
ovaries of 31. cirriferum and belli. At the periphery of the organs, 
especially on one side, young Clusters of oocytes with adhering ac- 
cessory cells are breaking away from the ovarial mass and falling 
into the cavity of the uterus. 
This stage of M. pulvinar would correspond, so far as the 
female reproductive organs are concerned, to stages 4 or 5 of 
M. cirriferum^ but the male organs of the entoparasitic species are 
in a stage which would probably lie between stages 9 and 10 of 
M. cirriferum. 
Stage 3. 1.7 mm long. This stage I bave not seen, but 
Prouho was fortunate enough to find a specimen which must belong 
bere. He describes it very briefly: »Les deux sexes doivent s'associer 
de très benne heure, car j'ai observé une jeune femelle de 1.7 mm 
