36 MaMxMary apparatus of the mammalia 



It seems to me that such an assumption is 

 to be rejected entirely. In the first place it 

 strikes one as very strange that these epidermal 

 growths should appear so early in the em- 

 bryonic life, while the material so accumulated 

 is not turned to account till very late in the 

 post-embryonic life. Just as little could we 

 understand, on this assumption, the part taken 

 by the cutis in building up the primary- 

 primordia and its relations to the skin-muscle, 

 and the vascular system. Above all, it w^ould 

 be unintelligible w^hy the material once accumu- 

 lated should at the end of the embryonic 

 period show so retrograde a development that 

 a new budding process should have to take 

 place in the transformation of the primary - 

 primordia into the gland areas. These con- 

 siderations, it seems to me, contradict such 

 a conception, and have led me to suggest 

 another conclusion — namely, that the primary- 

 primordia represent rudiments of organs which 

 long ago in the ancestors of the Echidna took 

 the place of the later gland areas. The very 

 early appearance of these structures testifies 

 to their phylogenetic age ; and that we are 

 dealing with rudiments is indicated by their 



