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- 
