HOW THE MAMMALS DEVELOPED 193 



ing entirely different from the clothing of any other 

 animal in the kingdom, and have warm blood, which 

 is found nowhere else except among the birds. But 

 particularly their method of producing their young 

 seemed so entirely different from that of any other 

 group that here a special creation was deemed abso- 

 lutely necessary. 



Other young creatures are produced from eggs laid 

 by the parent and subsequently hatched. The young 

 of the mammals are born alive and comparatively 

 well developed. In addition, their first food, the milk 

 of the mother, is so entirely different from the food 

 of any other creature that this again seemed to in- 

 volve a separate creation. Gradually we have come to 

 understand the whole matter of reproduction very 

 much better. Minute and careful dissections of rab- 

 bits, of dogs and cats, of animals slaughtered for food, 

 with occasional post-mortem examinations of human 

 beings in various stages of the development of the 

 young, leave us no longer in doubt concerning the 

 main features of the process. The better we come 

 to understand it the more clearly it becomes evident 

 that in the development of the mammals we have no 

 new procedure, but, as in so many other activities, 

 new developments of an old process. 



There are two entirely different methods by which 

 new animals and plants may arise. One sees some- 



