67 



the separate sexes of Asplanchna Brightwellii. The author of this 

 memoir soon afterwards discovered a second species of the same 

 genus (A. priodonta) with a like dioecious character ; and more 

 recently Dr. Leydig has added a third (A. Sieboldii), which does not 

 differ in this respect from its congeners. 



Dr. Leydig plausibly conjectures that Enteroplea of Ehrenherg is 

 the male sex of Hydatina, that Notommata granularis is the male 

 of N. Brachionus, and that Dialena granularis of Weisse is the male 

 of D. Catellina. 



The author of the present memoir has ascertained from his own 

 observations that the sexes are separate also hi Braehionus Pala, 

 B. rubens, B. amphiceros, B. angularis, B. BaJceri, B. Dorcas, 

 B. Miilleri, Synchceta tremula, Polyarthra platyptera, Sacculus 

 viridis, and Melicerta ringens. The males of these species, which are 

 here described in detail, differ so greatly from the females in form, 

 size, and structure, that they could not have been supposed to 

 belong to the same genera, or even families, if their parentage had 

 not been distinctly determined. 



One of the most remarkable characters of male Kotifera is the 

 absolute and universal atrophy of the digestive system. No mastax, 

 jaws, resophagus, stomach, or intestines occur in any example of 

 any species. Another peculiarity is the great disparity between the 

 sexes. In every observed case the male is inferior in size and in 

 organization to the female. 



The muscular system is well developed in the males of Hydatina, 

 Asplanchna, and Brack. Miilleri. The frontal cilia are in general 

 greatly developed in this sex, the result of which is seen in the 

 energy and rapidity of its locomotion. In most instances the great 

 occipital ganglion is distinct, with a red eye seated on it ; and the 

 latter is almost always present, even where the ganglion cannot 

 be defined. The lateral convoluted threads appear in Hydatina, 

 Asplanchna, and Brack, dorcas ; and in Aspl. Brightwellii they are 

 accompanied by tremulous tags, and by a contractile bladder. 



Irregular masses of opake substance are almost constantly present 

 in male Rotifera. This substance Dr. Leydig considers a urinary 

 concretion. 



In all cases the abdominal cavity is occupied by a capacious sperm- 

 sac, from which spermatozoa are forced out by pressure. The out- 



