260 HEREDITY AND ENVIRONMENT 



isms there must have been differences in the 

 constitution of the germ cells from which they 

 developed. For every inherited character 

 there must have been a germinal cause in the 

 fertilized egg. This germinal cause, whatever 

 it may be, is often spoken of as a determiner 

 of a character. But the character in question 

 is not to be thought of as the result of a single 

 cause nor as the product of the development 

 of a single determiner; undoubtedly many 

 causes are involved in the development of 

 every character, but the differential cause or 

 combination of causes is that which is peculiar 

 to the development of each particular 

 character. 



Again it is not necessary to suppose that 

 every developed character is represented in the 

 germ by a distinct determiner, or inheritance 

 unit, just as it is not necessary to suppose that 

 every chemical compound contains a peculiar 

 chemical element ; but it is necessary to suppose 

 that each hereditary character is caused by 

 some particular combination of inheritance 

 units and that each compound is produced by 

 some particular combination of chemical ele- 



