THE PLACENTA OF ELEPHAS AND HYRAX. 97 



No one, probably, would be inclined to object to the associa- 

 tion of the orders just mentioned into one great division of the 



Fig. 47. 



Fig. 47. A foetal cotyledon, (T 2 , half separated from the maternal cotyledon, C 1 , ot a Cow. 

 Ch, chorion. U, uterus (after Colin). 



Monodelphia, characterised by its placental structure. But such 

 grouping leaves several important points for discussion. The 

 Elephant has a zonary placenta,* and the genus Hyrax has been 

 known, since the time of Home, to be in like case. Hence, as 

 the elephants are commonly supposed to be closely allied with 

 the Pachydermata, which possess diffuse, non-deciduate placentae, 

 and as Hyrax is now generally, if not universally, admitted into 

 the same order as the Horse, which has a diffuse, non-deciduate 

 placenta, it is argued that placental characters do not indicate 

 natural affinities. A question, indeed, arises, which has not 

 been answered by those who have described the placentae of 

 Elephas and Hyrax. Is the placenta of these animals simply a 

 zone-like arrangement of villi or cotyledons, in connection with 

 which no decidua is developed, or is it a true deciduate placenta, 

 resembling that of the Carnivora in the essentials of its internal 

 structure as in its external form ? I have satisfied myself that, 

 in both these animals, the placenta is as truly deciduate as that 



* " Description of the Foetal Membranes and Placenta of the Elephant," by 

 Professor Owen. Philosophical Transactions, 1857. 



H 



