DKVKLOPMENT OF MAESUPIUM 



79 



There can, therefore, be no question of homol- 

 ogy between the incubatorium of the Mono- 

 tremes and the marsupium of the Didelphia. 



^f0 // // .^. -^' 



_bm 



Fig. 30a. — Transverse Section of Trichosukus. x 60. 



Fig. 30b. — Transverse Section of "Trichosurus 



VULPECULA." X 45. (BrESSLAU.) 

 ma, Primary-primordia ; rnt, marsupial pocket ; bm, pouch muscle. 



If, hitherto, such an assumption has always 

 been made as a matter of course, the explana- 

 tion is to be found in the great apparent 

 similarity of these two organs in the adult 



