358 



GENERAL ZOOLOGY 



adaptation. As to their general character, adaptations "are 

 primarily for the good of the species; they are beneficial to indi- 

 viduals only so far as these individuals are essential to the welfare 



Fig. 200. — Black swamp-wallaby of Australia carrying young in the marsupium. 

 {From Shall, La Rue, and Ruthven, Animal Biology.) 



of the species; and they often are injurious or destructive to the 

 individual, but since the welfare of the species is usually identical 

 with that of the constituent individuals, the destructive or 

 injurious effect is not obvious unless the good of the species 

 demands the sacrifice of individuals" (W. K. Brooks). 



