294 Dr. F. Leydig on Hydatina senta. 



bodies as fill the stomachal cells of all Rotatoria^ — thus furnish- 

 ing a distinct indication of its nature. 



In order to trace the further relations of the rudimentary in- 

 testinal canal, regard must at the same time be had to the testis, 

 which is situated in the hinder section of the abdomen. This 

 organ (PI. VIII. figs. 3j 4, c^c) forms an oval sac, the walls of 

 which are, however, by no means, as Cohu describes them, " very 

 thick and muscular,^' but, on the contrary, formed of a thin 

 membrane. AVhat the naturalist just mentioned calls the " very 

 thick and muscular walls" is the continuation of the rudimentary 

 intestine : we see this soldered to the testis, and by this means 

 an apparent second envelope of the organ is produced. Some 

 band-like filaments pass from this envelope to the skin for 

 the purpose of attachment. They are, however, no more con- 

 tractile (here also Cohn makes an opposite assertion) than the 

 entire rudimentary stomach which surrounds the testis. The 

 testis itself and its contents, as well as the efferent duct and its 

 accessory glands, display the greatest similarity with what I 

 have described in Notommata Sieboldii, only that everything, 

 down to the parts of the tissue, is smaller in Enteroplea. The 

 spermatozoa (fig. 5), as in Notommata, are of two kinds : some 

 have a bacillar form, exhibit no movements, and are stiff; the 

 others consist of a body pointed before and behind, upon which 

 an undulating membrane rises like a crest. In many indivi- 

 duals all the spermatozoa, so long as they were enclosed in the 

 testis, remained quiet, and only began to move when they were 

 pressed out and brought in contact with w^ater ; then, however, 

 the movement became slower, and soon stopped altogether. 

 Another time the spermatozoa exhibited a swarming movement 

 even within the testis. 



Perhaps the spermatozoa undergo a further development 

 within the body of the female as soon as they are transferred 

 there by copulation ; at least, it is remarkable to me that the 

 seminal elements moving about in the abdominal cavity of cer- 

 tain females were much thicker at one end, and as it were had 

 a separated head, which was never seen in those pressed out of 

 the testis. In exact accordance with what was observed in No- 

 tommata, the motionless, bacillar spermatozoa lie in the testis, 

 especially at the point where the efferent duct commences, and 

 by their regular arrangement produce a radiate striation at this 

 point. I must directly contradict the statement that this " close, 

 parallel, longitudinal striation" occurring at the posterior end 

 of the testis, is due to " muscular fibres ;" the " striae" may be 

 pressed out as well as the rest of the contents of the testis ; and 

 in'this way we may convince ourselves that the bacillar sperma- 

 tozoa were the cause of the striation. The wall of the testis, as 



