54 MAMMARY APPARATUS OF THE MAMMALIA 



his previous ideas, and because it explained the 

 marsupium as having developed from the 

 fusion of the mammary pouches in the same 

 wav as the incubatorium of Echidna. Thus 

 Gegenbaur and Klaatsch believed that they 

 could trace back the mammar}' apparatus of 

 the Marsupialia to conditions existing in the 

 Echidna. The glands, however, which provide 



Fig. 18.— Marsupium of Fully Developed Tricho- 

 surus, showing the two nipples, p, each sur- 

 ROUNDED BY A Marsupial Pocket. 



the nutritive fluid for the vouna: were, in their 

 view, of diphyletic origin, because the mam- 

 mary glands of the Monotremes, tliey held, had 

 developed from the sweat glands, whilst the 

 milk glands of the rest of the Mammals, in 

 their view, developed from the sebaceous 

 glands of the hairs of the bottom of the 

 mammary pouches. 



