Dr. F. Leydig on Hydatina senta. 295 



has been already mentioned, is destitute of contractility ; but it 

 may be observed that the eflferent duct is capable of strong con- 

 tractions, and I also refer its thick wall and the transverse stria- 

 tion visible on the latter, to a muscular membrane. Cilia exist 

 in the interior of the duct ; they are longest at the orifice, and 

 the latter is situated on the first segment of the tail. On the 

 outside of the efferent duct there are some glandular bodies, 

 which might be compared with accessory glands, perhaps a pro- 

 state, as was also done with regard to Notommata. 



The same dark aggregations of granules (PI. VIII. figs. 3, 4, b) 

 which are observed in many embryos and young animals of the 

 Rotatoria occur in Enteroplea ; they usually form two masses, 

 but sometimes three ; the granules vary greatly in number and 

 size, and sometimes we see accumulations of small globules; 

 sometimes they consist of a few single, large fragments. From 

 their optical and chemical characters, I had pronounced these 

 granules to be uric concretions, and expressed the opinion 

 that such accumulations of granules or crystalline formations 

 occurring, except in the males, only in the embryonic stage 

 and in early youth, might have the signification of a primor- 

 dial kidney. Cohn, on the contrary, thinks that " this whole 

 hypothesis falls with the proof that in Enteroplea the vesicle 

 with the dark granules stands in no sort of connexion with the 

 intestine, nor indeed can do so, as no intestine exists, and that 

 it is rather firmly adherent to the outer wall of the testis, which 

 I could prove beyond a doubt." And yet I cannot avoid re- 

 marking that, as is evident from the above description of the 

 testis, Cohn's "undoubted proof ^^ is an error. For the clear 

 space containing the dark granules is not "adherent" to the 

 true wall of the testis, but to that outer envelope which repre- 

 sents the rudimentary stomach and intestine ; or, more properly 

 speaking, the clear space enclosing the concretions belongs to 

 the abortive alimentary canal itself, which extends from the 

 notch of the rotatory organ to the cloacal opening; so that 

 Enteroplea displays the same characters as the other Rotatoria, 

 although this is in complete opposition to the description given 

 by Cohn. i\Iy opinion that the granules in question are uric 

 concretions, is of course no more strongly supported by the 

 position of matters detected in Enteroplea than before, but the 

 objection raised by Cohn appears to be removed. The opinion 

 first put forward by ^Yeisse, which is also favoured by Cohn, 

 that the granules are the remains of unused yelk-masses, I must 

 reject, without taking other reasons into account, if only because 

 the vitelhne elements and the granules in question have no 

 resemblance to each other, but are perfectly different things. 



In conclusion, something may be stated regarding a parasite 



