1881.] On the Female Organs, Sfc, of the Racoon. 



325 



permit tidal friction to be the principal feature in their evolution, 

 whilst its effects are less striking in the other planets. 



Amongst other points discussed are the comparative speeds of 

 rotation of the several planets, and the probable effects of the genesis 

 of a satellite on the course of change afterwards followed by the planet. 



The paper ends with a review of the solar system, in which it is 

 shown that the tidal hypothesis is a means of co-ordinating many 

 apparently disconnected phenomena, besides giving a history of the 

 earth and moon since the origin of the latter. 



These investigations afford no grounds for the rejection of the 

 nebular hypothesis, but while they present evidence in favour of the 

 main outlines of that theory, they introduce modifications of con- 

 siderable importance. Tidal friction is a cause of change of which 

 Laplace's theory took no account, and although the activity of that 

 cause is to be regarded as mainly belonging to a later period than the 

 events described in the nebular hypothesis, yet its influence has been 

 of great, and in one instance of even paramount importance, in de- 

 termining the present condition of the planets and of their satellites. 



IV. " On the Female Organs and Placentation of the Racoon 

 (Procyon lotor)." By M. WATSOX, M.D., Professor of 

 Anatomy, Owens College, Manchester. Communicated by 

 Professor Huxley, Sec.R.S. Received December 30, 1880, 



(Abstract.) 



The paper contains an anatomical description of the female organs 

 and placenta of the racoon. The specimen examined contained but a 

 single foetus, which was lodged in the right horn of the uterus. The 

 uterine mucous membrane of the unimpregnated horn was richly sup- 

 plied with glands, which presented the usual structure. In the non- 

 placental area of the gravid horn these glands, although present, were 

 evidently undergoing degeneration and were with difficulty recognised, 

 and then only in a fragmentary condition ; whilst in the placental area 

 of the uterine mucous membrane these glands had entirely disappeared. 



The author's observations upon the placenta of Procyon lotor show 

 that in respect of this organ : — (1.) Procyon agrees with all other 

 carnivora, in which that organ has hitherto been examined, in the pos- 

 session of a zonary or annular placenta. 



(2.) That Procyon agrees with all of these in the mode of interlock- 

 ing of the foetal and maternal portions of the placenta and in the 

 consequent deciduate character of that organ. 



(3.) That Procyon agrees with the members of the plantigrade sec- 



