Huxley's views on phylogeny 137 



independently of the rest of the Mammals 

 from viviparous ancestors. 



Sauropsida. Monotremata. Placentalia. Marsupialia. 



Viviparous 

 Forms. 



If now we bring the conclusions derived 

 from the study of the mammary apparatus 

 into relation with these views, it becomes 

 evident that they speak as clearly against the 

 last two sets of views as they do for that of 

 Huxley. The fact that the development of 

 the mammary apparatus of the Monotremes 

 and Marsupials begins with primary-primordia, 

 identical in the two, and that mammarv hairs 

 are present in both, proves along with other 

 structural features which they have in common 

 that there can be no question of their diphyletic 

 origin. And as concerns the Trophoblast theory 

 of Hubrecht, it need only be remarked that it 

 is against all morphological principles to attach 

 such value to a purely embryological and no 

 doubt adaptive feature, and to leave out of 

 account all other structural characteristics. 



Just as certainly must we regard that other 



