154 THE THEORIES OF EVOLUTION 



plasm will be much weaker. Being weaker they will 

 secure less food, so that more food will go to the other 

 determinants; in the following generations, they will 

 become weaker and weaker, until the organ is com- 

 pletely obliterated. In other words, panmixia is an 

 indispensable preliminary to this degeneracy; the 

 struggle for food between determinants completes the 

 process. 



Germinal selection is at the very basis of natural 

 selection and the conception of determinants is neces- 

 sary to explain the latter. The idea of selection must 

 be made to include all living units without restriction. 

 "If the principle of selection operates in nature at 

 all, it must do so wherever living units struggle to- 

 gether for the same requirements of life, for space 

 and food, and these units need not be persons, but 

 may represent every category of vital units, from the 

 smallest invisible units up to the largest. ... It 

 seems best to assume and distinguish between four 

 main grades of selective processes corresponding to 

 the most outstanding and significant categories of 

 vital units, namely: germinal, histonal, personal, and 

 cormal selection." 



" Histonal selection includes all the processes of se- 

 lection which take place between the elements of the 

 body (soma), as distinguished from the germ plasm, 

 of the Metazoa and Metaphj^ta, not only between the 

 tissues in the stricter sense, but also between the 



