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
BioStor
