24 ARKIV FÖR ZOOLOGI. BAND 14. N:0 13. 



rhabdites. It may here be remembered that some other 

 features, even if they are not very important, are not typical 

 for the polyclads, such as the small size of the body, the 

 feeble development of the muscularis, and the reduction of 

 the number of ovaries. 



I have observed true nematocysts in the parenchyma, 

 but not toany considerable extent. In most cases the capsules 

 still Gontain their (coiled) spiral threads and are thus intact. 

 They occur also in the lumen of the gut-branches and in the 

 intestinal epithelium, which affords evidence that they really 

 are of foreign origin and introduced with the food. They 

 are infrequent in the external epithelium. 



The number of subdermal mucous gland cells is not ex- 

 cessively great. 



The pharynx is folded to the same extent as that of 

 Ghro7noplana. The intestine is also similar to that genus. 



Generative organs. 



The testes, which possess well-marked membranae pro- 

 priae, are always ventral to the gut-branches, numerous, and 

 never large (only 60 [i. or less in diameter). 



As the sections were stained with Ehrlichs Haematoxylin 

 and Pikro-Fuchsin, the most vivid contrast was obtained 

 between the blue-stained germinative layer and the yellow 

 yolk of the mature oocyte, in which the former layer was 

 imbedded. 



The ovaries are remarkably few and also situated ven- 

 trally to the digestive system. They occur among the testes, 

 never situated more ventrally than these. When an ovary 

 possesses a ripe oocyte, and never more than one is present 

 at the same time in one ovary, a peculiar aspect is given to 

 the ovary. The germinative zone is placed in a hollow of 

 the ripening oocyte. A section of the ovary shows the oocyte 

 crescent-shaped and thus the ovarial cells of younger stages 

 are to a great extent surrounded by the more or less ripe 

 oocyte (text fig. 6, Plate 2, fig. 2 and 6). The ovary in 

 itself is strictly spherical. The position of the germinative 

 zone in the ovary varies, being dorsal, lateral or ventral. 

 When an ovary contains a fully ripe oocyte the germinative 

 zone is insignificant in comparison with this egg. The small 

 ovarial cells are of about the same size (text fig. 6). The 



