Individual Variation 245 



modest. But these are, in each instance, only degrees 

 of the same hereditary characteristic, or the same trait 

 of character. And such more or less differing stages 

 of development of the same inner units we represent to 

 ourselves as the entities which are exchanged by the nu- 

 clear threads. 



Individual differences are thus not included in the 

 type of the species. They form deviations from this 

 type, and are conditioned by causes which were formerly 

 generally described as conditions of nutrition, but now 

 more frequently as environment. Under these influences 

 every character can develop more or less strongly than 

 the average type. And the environment, provided it re- 

 mains constant during the entire period of development, 

 must affect all the unfolding characters in the same way. 

 If it is favorable it furthers all parts of the body and all 

 mental gifts, if it is unfavorable it has the opposite effect 

 on all of them. Not, by any means, to the same degree 

 upon all of them : that does not depend upon the environ- 

 ment but upon the units themselves; this, however, can 

 not lead to essential differences between separate individ- 

 uals. But our supposition of such a uniform environ- 

 ment would probably be met with only in the rarest of 

 cases. And, as soon as it changed, it would influence 

 one individual differently from the others. Moreover 

 the characters do not unfold simultaneously, but success- 

 ively, the higher ones for the most part later than the lower 

 ones, mental characters later than those of the body, the 

 reason later than the memory. And all those wheels 

 work into each other so that small deviations will rather 

 tend to become greater than to be equalized. Though 

 children of the same parents but of different age might, 

 during their entire youth, live under the same circum- 



