42 DEVELOPMENT AND HEREDITY. 



forces outside of the organism or to energy in the 

 hving matter which composes the organism. A 

 very minute portion of energy and matter is suf- 

 ficient to compose a germ ; all the rest of the 

 matter and energy which has to be added before 

 the germ becomes an adult organism must accord- 

 ingly be received from the environment. Thus we 

 see at once how dependent each individual organ- 

 ism is upon its environment. A few illustrations 

 will make clearer the relation of the organism to 

 the forces of its environment. 



Among the higher animals all individuals begin 

 their existence in the same manner. Each one is 

 dependent on the energy of heat for its first devel- 

 opment, and each is dependent on the peculiar 

 combination of forces which make up its nutriment. 

 The peculiar nutriment, and also the other pecul- 

 iar environment of each individual, such as the 

 medium in which it exists, are absolutely essential 

 to its development. It is, perhaps, a general idea 

 that all this peculiar environment has merely a 

 passive value for the germ's development ; and 

 that when the germ is removed therefrom it dies, 

 not for want of the forces which have sustained 

 its life, but because of the fatally aggressive action 

 of a new environment. A moment's reflection 

 must show how unwarranted such an idea is. The 



