DEVELOPMENT IN ECHIDNA 



15 



mammary apparatus, thus refuting Ruge's 

 views. 



Let me now sketcli the actual stages in the 

 development of the mammary apparatus in 



aur 



ma 



Fig. 5.— Echidna: Semon's Embryo, Stage 42. 



VM, Primai-y-primordium ; aur, beginnings of the outer ear. 



Echidna so far as I could observe them in the 

 material at my disposal. 



Whereas Klaatsch and Ruge believed that 

 the development of the mammary apparatus 

 began only after the hatching of the young, 



