342 The Morality of Nature 



change is not too abrupt, the seemingly steadfast germ 

 shows a different evolution. This then is one source of 

 variation. Change of stimulus, or change of activity, awake 

 the latent responsiveness of the germ-plasm, to new effort 

 which is the basis of adaptability. It is for this reason that 

 every higher animal species having constancy, secures it by 

 a preserved environment. The conditions must remain na- 

 turally constant for the external budding, single-celled crea- 

 ture, or those of vegetable structure; but the highly devel- 

 oped animal guards them for its historical embryology, and 

 preserves historical environment to preserve constancy of 

 development. For this reason the mammalian germ is de- 

 veloped in the womb, deep and secure in the structure of the 

 parent; where conditions for the rapid reminiscent growth 

 of embryonic life, are preserved, as they were when that 

 embryo was a primitive thing. The fish eggs can continue 

 to fertilize in open exposure to the sea, and the sea urchin 

 can even fecundate in little more than sea water itself. Birds 

 and reptiles produce eggs which are fertilized and partially 

 developed, with an organized egg structure, to carry yolk 

 food, and suitable medium and environment, during a long 

 and elaborate process of growth outside the body of the 

 parent. When warmth is applied the morphology is then 

 determined, not by the germ cell alone but in part by its 

 prearranged nutritive environment. And in mammals this 

 destiny of development is fulfilled under the influence of the 

 environment provided by the structure and secretions of the 

 parent. 



The method by which evolution reaches this situation is 

 revealed by embryology. It is seen that by the time that the 



