NIPPLE DEVELOPMENT OP MARSUPIALS 83 



therefore form " eversion nipples," as we may 

 term them (Fig. 31, b - d). In all Australian 



Fig. 31. — Nipple Development of the Marsupials. 

 (Bresslau. ) 



I. Primary sprouts (primordia of mammary hairs). 

 II. Secondary sprouts which gire rise to milk glands. 

 III. Tertiary sprouts (primordia of sebaceous glands). 



a, Nipple primordium ; b-d, stages of eversion nipples ; e, transition 

 between eversion nipples and proliferation nipples ; f-g, stages of 

 proliferation nipples. 



Marsupialia their development proceeds as 

 follows : The knob-shaped primordia are con- 



