134 MAMMARY APPARATUS OF THE MAMMALIA 



the oldest organs of the mammary apparatus 

 stood in the way. For it had to be assumed 

 that the Placentalia were derived from pouch- 

 bearing forms, naturally with loss of the 

 marsupium. 



And so we have an explanation of the fact 

 that investigators have always been on the 

 lookout for pouch rudiments in the Placentalia, 

 and have accordingly easily believed in the 

 discovery of a whole series of such. It is 

 not necessary, however, to waste time over 

 these assumed pouch rudiments, for we know 

 that such cannot exist, since a pouch stage 

 was not included in the phylogenesis of the 

 Placentalia. 



In conclusion, it remains for us to discuss 

 the affinities of the three sub- classes of the 

 Mammals, on the basis of our knowledge of 

 the development of the mammary apparatus. 

 But in so doing we shall not neglect the 

 phylogenetic facts resulting from the study 

 of the entire ora^anization of the Mammals. 

 This is the more necessary, since disregard of 

 such an obvious principle has often led to 

 the construction of erroneous phylogenetic 

 theories. We have indeed an excellent 



