DEVELOPMENT IN MARSUPIALIA 55 



After what has been written in the preceding 

 chapter, a criticism of these views is scarcely 

 necessary. For it is evident that nothing can 

 be more fatal to a mammary-pouch theory 

 than the proof of the non-existence of mam- 

 mary pouches ! Eliminate mammary pouches 

 from the cleverly combined ideas of Gegenbaur 

 and Klaatsch and it is seen at once that they 

 rest upon no firm basis of observation. And if 

 we wish to replace the Gegenbaur-Klaatsch 

 theory by a new and better established one, we 

 must start by carefully examining the develop- 

 ment of the mammary apparatus of the Mar- 

 supialia at every stage and in as many different 

 forms as possible. 



My thanks are due to the authorities of 

 many public and private collections, in and out 

 of Germany, for providing me with a very rich 

 material for this purpose, comprising nearly 

 400 specimens of the young of the various 

 families of marsupials. And yet for a long 

 time I was not able to come to a conclusion, 

 because of the absence from my material of 

 uterine embryos, which alone would have 

 enabled me to observe how the development of 

 the mammary apparatus begins. I owe the 



