85 273 



At all events in R. cylindricus a well developed antenna; a retrocerebral oif^an has 

 hitherto not been found, but always a dorsal antenna, and in the male of H. ci/lin- 

 driciis two lateral ones, symmetrically situated (in the female asymmetrically). An 

 excretory organ may often have been overlooked ; it is only found in R. cijliiulricus. 

 The testis is globular, a prostata gland is perhaps always present; peculiar is the 

 long, thin, protrusile, chitinised penis-lube, ending in a disc without a wreath of cilia. 

 No trace of alimentary canal found. The muscle system is slightly developed. Whereas 

 the females are highly asymmetrical, the males are symmetrical animals. 



Euchlanidæ. 



The family comprises the two genera Euchlanis and Diplois. The males of Üiplois 

 are unknown. As far as I know, only Cohn has seen and given a more thorough 

 description of a male of an Euchlanis (E. dilatafa). The species of the genus Euch- 

 lanis are even in the female sex very difficult to distinguish from each other, and 

 a revision most necessary. The main characters are to be found in the size, in the 

 relation between the dorsal and ventral plate, in the anterior and posterior borders 

 of the cai'apace, in the number of teeth in the unci and in the number of the long 

 hairs on the foot. 



At different times I have seen the males of the four species E. dilatata Ehrbg. 

 E. oropha Gosse (= parva Rouss.). E. triquetra Ehrbg. and E. lijra Huds. As the 

 males are almost all of the same size, and the posterior and anterior borders are 

 subject to great variation and difficult to study upon dead animals, as further the 

 mastax is wanting, and I have never been able to find the long hairs on the foot 

 of the male, it will be understood that it is very difficult to distinguish the males 

 from each other; only the male of E. triquetra is always recognisable. 



Euchlanis dilatata Ehrbg. 



Male: Cohn 1858, p. 290. 

 Weber 1898, p. 580. 

 Tab. IV, fig. 1, Tab. V, fig. 5. 



Cohn (1858, p. 290, Tab. XIII, fig. 5 — 7) gives one of the best descriptions and 

 drawings of a male Rotifer which has hitherto been published. 



The male is remarkably large, tieing 260 a«, almost as large as the female, the latter being 

 often only 290 A*. Tlie body is the same as that of the female but the male is much more hyaline. 

 The carapace, tlie wheel-organ and the foot are formed in full accordance with these organs in 

 the female. On the other hand the whole alimentary canal is lacking. The retrocerebral organ, 

 which is remarkably correctly drawn, is regarded as a brain; no lateral organs; but the dorsal 

 antenna, indicated as "sporn", has been observed. So also are the excretory canals with three 

 or four vibratile tags; it is stated that there exists a contractile vesicle. The testis is described 

 as a long sac with elastic walls. The band which runs from the testis and forwards and which 

 Leydig regards as a rudiment of the intestine, is described. A prostata is found. Penis is 

 traversed by a canal, coated with cilia and ends on the first joint of the foot. The sack with 

 light refracting grains over the testis has only been observed in very young animals. Mating 

 process not observed. 



