The Mammal. 127 



spring, — though there are many apparent excep- 

 tions to this rule, complexity being more impor- 

 tant than actual size. 



If it is true that all mammals develop from the 

 egg, what then becomes of this mammalian egg- 

 cell? 



Is it deposited in a cleft in the bark of a tree, or 

 consigned to the cold guardianship of river or sea? 

 By no means. It is not even deposited with pa- 

 rental care in a nest, and there guarded during its 

 slow change. 



Or rather it is deposited in a nest, but the nest 

 is not made of twigs, as is the nest of the bird, or 

 of silk, as is the egg-nest of the spider; this nest is 

 an adaptation of the reproductive tissue itself, and 

 lies securely cherished within the parental form. 



The mammalian egg, like all others, ripens and 

 leaves the ovary periodically, the frequency with 

 which this occurs depending, as a rule, upon the 

 size of the animal, — it happening oftener in the 

 smaller ones. 



At this time, the activity of the ripe egg-cell and 

 of the reproductive centres is communicated to the 

 whole structure ; there is a corresponding exhilara- 

 tion and awakening throughout, and there goes 

 forth that desire of the cells for added life which 

 characterized the fish at the reproductive season, 

 and which characterizes all life. The whole being 

 is charged with a new and powerful vitality; it be- 

 comes like a magnet in its attractive power to the 



