THE MAMMAEY APPARATUS 

 OF THE MAMMALIA 



CHAPTER I 



THE Mammalia are so called because they 

 present a highly developed organic system 

 for the nourishment of their young — the mam- 

 mary apparatus — and it might be presumed that 

 this apparatus would be uniformly developed in 

 the whole group like the other principal charac- 

 teristic, the hair. But that would be a mistake. 

 One finds so many important differences in 

 the development of the separate parts of the 

 mammary apparatus in the various orders of 

 Mammals, that up to the present it has been 

 impossible to compare them properly and to 

 show their relationships one with another. 



None of the many attempts to explain the 

 phylogeny of the mammary apparatus, or parts 

 of it, has been able to withstand searching 

 1 



