EXTENSION OF EVOLUTIONARY THEORIES 337 



Irregularities in the food-supply may also lead the 

 determinants to vary in quality, and so give rise to 

 qualitative variations in the parts of the body 

 subsequently. This is believed to be brought about 

 by a difference in the growth within a determinant of 

 the many biogens that compose it; this leads to an 

 alteration of the structure of the determinants. 



Germinal selection thus seems to explain the dis- 

 appearance of useless organs. These also have, of 

 course, one or rather several^ determinants in the 

 germ-plasm. And while decreasing determinants of the 

 necessary organs are rooted out with the animals they 

 are in, as they are insuflficiently equipped for the 

 struggle for life with their undersized necessary organs, 

 on the other hand the decreasing tendency is preserved 

 in useless organs, because their possessors are not 

 extinguished by selection. In this case enlargements 

 of useless determinants are cut off. Such growing 

 determinants take the nourishment away from the others, 

 and cause them to be smaller. But they must not 

 become smaller, since they build up important and 

 indispensable organs. Hence rising tendencies in the 

 determinants of useless organs are cut off, and only 

 those are preserved that keep them down and reduce 

 them in size. In this way the determinants and their 

 organ must gradually disappear within the species. 



Here we have the principle of selection. There is 

 a kind of struggle for nourishment among the deter- 

 minants in the germ. If one of them has become large 



^The eye, for instance, must have several determinants, otherwise 

 each part could not vary of itself. Hence there must be an immense 

 number of determinants in the germ. 



V 



