72 HEREDITY 



inent of the particular organ or cell under con- 

 sideration. There can be no philosophic defence 

 of any other course than this. We must be per- 

 mitted to exercise our faculty of ideal isolation on 

 any object or any portion of any object. 



Now, when we come to concrete questions in 

 biology, we find the importance of having clearly 

 understood the use of the term environment. For 

 instance, in the vulgar use of the term we speak of a 

 dog (as an indivisible entity) and its environment ; 

 and we note that certain changes may occur in the 

 dog's body as the result of its converse with the 

 environment. But in the dog's body there are a 

 number of germ- cells, which Weismann has taught 

 us to consider as independent, as being not really 

 part of the dog at all, but an immortal race of 

 which the dog is the temporary trustee. Thereupon 

 it is said that the environment may affect the dog 

 but not its germ-cells. A corollary from the 

 doctrine of the " continuity " and " immortality " 

 of the germ-plasm is supposed to be the inviola- 

 bility of the germ-plasm. But when we proceed 

 to exercise the power already demanded and 

 mentally isolate the germ-plasm of the dog, set- 

 ting it up in antithesis to all else, we see that it 

 is necessary to regard the body of the dog as the 

 immediate environment of the dog's germ-plasm. 

 The question then is : In what manner, if at all, is 

 the germ-plasm of any individual organism affected 

 by its immediate environment — i.e. by the body of 

 the individual ? 



For the present we are assuming the correctness 

 of Weismann's contention as to the independence 



