OTHER THEORIES OF GERMINAL SELECTION 407 



Although his intorprctation of these determinants is not exactly 

 the same as our modern understanding of genes, it is a tribute to 

 his insight that he came so near to the fundamentals of the modern 

 theory. He cautions his readers that nothing can be learned 

 directly of the intimate structure of the germ plasm; this difficulty 

 has, of course, been partly removed by modcn-n cytology, although 

 we are still unable to see the genes in which we now believe so 

 firmly. 



The next step in his theory assumes that, since these particles 

 in the germ plasm are living matter, they are nourished, grow, and 

 multiply. We know no more about this matter than Weismann 

 did, but we must still admit that his opinion is soundly logical. 

 However minute the gene may be, or whatever may be the nature 

 of its organization, we cannot fail to regard it as living matter, 

 subject to the same fundamental laws that have been observed in 

 larger units. 



Weismann then assumed that irregularities occur in the nourish- 

 ment of the determinants and that they differ in their capacity 

 to make use of available food. As a result he supposed that some 

 would increase in vigor at the expense of others, and attain greater 

 expression of the structures which they produced in the body. 

 Such a modification of determinants would necessarily be cumu- 

 lative, for weakening would still further reduce the possibility 

 of a part's securing adequate nourishment. The result would be 

 a gradual modification of the characters of the organism, some 

 increasing and some decreasing in development. 



Criticism of Germinal Selection. At this point the unsound- 

 ness of the theory becomes apparent. We must consider that 

 most of the organisms with which we are concerned are normal 

 and lead a normal existence. There is every reason to believe 

 that in such organisms every part of the body is supplied with 

 adequate nourishment and that competition between the various 

 parts does not occur. Even in starvation the whole body starves 

 together; distribution of the available nourishment is made for 

 the greatest common benefit. When we consider the capacity 

 of individual determinants for securing available nourishment we 

 are dealing with hereditary quaUties; the very existence of a living 

 unit would demand suflficient ability to meet existing conditions. 



It is impossible to see how this theory can account for evolu- 

 tionary changes in organisms except on the basis of varying 



