Ro7jal Society. 333 



Cleveland LodgCj Yorkshire, whose indefatigable researches in 

 his neighbourhood have supplied me with many Lichens hitherto 

 unknown to our flora. 



Plate XI. fig;. 11. Thallus and arclcllae, nat. size. Fig. 12. The same, 

 magnified. Fig. 1."^. Vertical section of ardella. Fig. 14. Aseus 

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

 of TT^o 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 Dioecious Character of the Rotifera." By Philip H. 

 Gosse. 



Professor Ehrenherg, 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 AspUinchna BrightweUii. The author of this 

 memoir soon afterwards discovered a second species of the same 

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

 recentlv Dr. Leydig has added a third (^A. Sieholdii), which does not 

 differ in this respect from its congeners. 



Dr. Levdig plausibly conjectures that Enteroplea of Ehrenberg is 

 the male sex of Hydutina, that Notommata yranularis is the male 

 of i\'. Brachiomis, and that Diglena granulans of Weissc is the male 

 of J). CateUhia. 



The author of the present memoir has ascertained from his own 

 observations that the sexes are separate also in Brachiomis Pula, 

 B. rubens, B. amphiceros, B. angidaris, B. Bakeri, B. Dorcas, 

 B. Mill/eri, Sy/ic/iceta tremula, Folyarthra platyptera, Sacculus 

 viridis, and Melicerfa 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 

 anv 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 Ilydatina, 

 Asplanchna, and Brack. MiiUeri. 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 



