41 



show adaptation for the defense of the young, as the 

 marsupials, which have the large pouch on the abdo- 

 men for the reception of the young (see Australian 

 case.) Then come a series showing sex dimorphism, 

 or differences in the sexes. The ducks and fowls 

 show this most prominently, and in many insects it is 

 carried still further, in many forms one sex being 

 winged while the other is wingless, etc. Hardly a 

 beginning has been made in this series, which it is 

 hoped may be developed into several most interesting 

 collections. 



