Royal Society, W %'rW 333 



Cleveland Lodge, Yorkshire, whose indefatigable researches in 

 his neighbourhood have supplied me with many Lichens hitherto 

 unknown to our flora. 



t*LATE XL fig. U. Thallus and ardellse, nat. size. Fig. 12. The same, 

 magnified. Fig. 13. Vertical section of ardella. Fig. 14. Ascus 

 and sporidia. Fig. 15. Sporidia, highly magnified. Fig. 16. Scale 

 of -x4oo of an inch, magnified equally with the sporidia in figs. 5, 

 10 & 15, to show their real size. 



PROCEEDINGS OF LEARNED SOCIETIES. 



ROYAL SOCIETY. 



April 3, 1856.— Sir Philip de Malpas Grey Egerton, Bart., V.P., 

 in the Chair. 



"On the DicEcious Character of the Rotifera." By Philip H. 

 Gosse. 



Professor Ehrenberg, in his descriptions of this class of animals, 

 assumed them to be in every case hermaphrodite. His conclusions 

 remained unchallenged till 1848, when Mr. Brightwell discovered 

 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 tts congeners. 



Dr. Leydig plausibly conjectures that Enteroplea of Ehrenberg is 

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

 of N, BrachionuSy and that Biglena granularis of Weisse is the male 

 of D. Catellhia. 



The author of the present memoir has ascertained from his own 

 observations that the sexes are separate also in Brachionus Pala, 

 B. ruhensy B. amphiceros, B. angularis, B. Bakeri, B. Dorcas^ 

 B. Mulleriy 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 Rotifera is the 

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

 jaws, oesophagus, 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 i^ 

 organization to the female. "' 



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

 Asplanchna, and Brack. MUlleri. 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 



