POLYCLAD FLATWORMS — HYIVIAN 547 



General characters: This is a very small species, of broadly oval 

 form, about 2 mm. long and about half as wide (fig. Id), broadest at 

 the middle and decreasing slightly to the rounded ends. It is white 

 with sprawling black marks in a longitudinal row along each side but 

 some of these are associated with developing clusters of eggs. Eyes 

 are totally wanting. In the center is seen a small ruffled pharynx and 

 behind this, directed backwards, the large prostatic vesicle, posteriorly 

 encased in a conical pointed penis stylet. Behind the tip of the stylet, 

 the cement glands of the female apparatus are noticeable. Groups 

 of eggs in various stages of development are evident in the interior and 

 a cluster of a few very large, presumably ripe eggs was conspicuous 

 in most specimens at a level between the pharynx and the prostatic 

 vesicle, on each side. These were presumably enclosed in the uteri. 

 They seem very large for the size of the worm. Branches of the 

 intestine, not shown in the figure, could be seen in the whole mount 

 radiating to the periphery and passing back to either side of the 

 prostatic vesicle. 



Histology: One specimen was mounted whole and the other four 

 were sectioned, two in the sagittal plane and two transversely. 

 Because of lack of proper fixation the histological condition was un- 

 satisfactory and yielded little definite information. Epidermis was 

 lacking everywhere but subepidermal musculature could be detected 

 here and there. The whole interior appeared as a fibrous mesh con- 

 taining nuclei. Even branches of the intestine were scarcely recogniz- 

 able. Ovaries and testes are relatively large and about fill the thick- 

 ness of the body, hence cannot be said to be either dorsally or ventrally 

 located. The large eggs noted in the whole animal were found to be 

 very yolky, filled with large eosinophilous spheres and covered with a 

 layer of dark bodies. The brain could not be definitely identified 

 either on the whole mount or in the series of sections. 



CopuLATORY apparatus: This was satisfactorily worked out on one 

 series of sagittal sections and is shown in sagittal view in figure le. 

 The large oval prostatic vesicle, of the free type, is the most conspicu- 

 ous part of the male apparatus. It has a fairly thick muscular wall 

 and a glandular interior of eosinophilous nature. It is oriented some- 

 what vertically with a forward slant; distally it continues with a 

 sharp bend as the penis papilla which has a horizontal orientation. 

 The elongate penis papilla is housed in a male antrum of the same 

 shape. At its distal end the penis papilla is encased in a sclerotized 

 cone taking the eosin stain that may be regarded as a penis stylet. 

 A cross section through this part of the penis papilla is shown in 

 figure If. The stylet is covered with a thin layer containing flattened 

 nuclei and is lined by a cuboidal epithelium continuous with the lining 

 epithelium of the unsclerotized part of the penis papiUa. Anterior to 



