Dr. F. Leydig on Hydatina senta. 293 



asserts that the obliquely funnel-shaped depression of the rota- 

 tory organ is wanting in the male. In animals which begin to 

 tire in their movements, we may perceive, with regard to the 

 form of the body, that the dorsal surface is somewhat arched, 

 and the ventral rather flat ; perfectly fresh individuals are con- 

 tinually contracting, and the body thus appears strongly folded 

 longitudinally. 



The muscles, the brain with the nerves, the contractile vesicle 

 with the vessels and tremulous organs, are essentially as in the 

 female, for which reason they will not be further mentioned ; I 

 refer the reader to fig. 3. The clavate glands in the tail also 

 are not wanting; but this difference is perceptible — they are 

 faintly notched several times on the margin, which is not the 

 case in the female. 



Dalrymple had observed in Notommata anglica, as I have done 

 in N. Sieboldii, that the male is entirely destitute of an alimentary 

 canal. The male animals possessed neither pharynx nor jaws, 

 oesophagus nor stomach. There was only an irregular aggrega- 

 tion of cells, which was regarded as the rudiment of the aliment- 

 ary canal. Of the male Hydatina also Cohn states, that in it (the 

 Enteroplea) the nutritive apparatus is completely wanting in all 

 its parts, and that not even the cellular rudiments of the above- 

 mentioned species of Notommata are to be detected. With this 

 view, however, I cannot altogether agree. It is true that, as 

 was already established by Ehrenberg, the Enteroplea is entirely 

 destitute of biting organs, and a developed tractus cibarius is 

 altogether wanting ; moreover, no solid nourishment taken from 

 without is ever observed in the transparent animal. But it may 

 be said with perfect certainty, that the alimentary canal exists in 

 an abortive state. Thus, the part which Cohn has characterized 

 as the suspensor testis, and Ehrenberg as the intestine, and which 

 the former author regards as a long and broad band, originating 

 from the anterior apex of the testis, and running transversely 

 through the cavity of the body towards the frontal region, is 

 undoubtedly a rudiment of the alimentary tube (Pl.VIII.fig.3,«), 

 as is shown both by its position and structure. When the ani- 

 mal is examined in profile, the anterior extremity of the rudi- 

 mentary intestine passes exactly towards that spot in the rotatory 

 organ where the buccal orifice is situated in the female ; pos- 

 teriorly, as will be mentioned immediately, it extends to the 

 cloacal orifice. As regards its more intimate conditions, we find 

 the rudimentary intestine, like other organs which have become 

 retrograde, more or less abortive in difi^erent individuals ; some- 

 times it is a clear, folded tube, without cellular parts ; in another 

 case it contains unmistakeable remains of the stomachal cells — 

 namely large vesicles, with aggregations of such yellowish-brown 



