EXPLANATIONS OF RETROGRESSION 109 



very little nutriment. Moreover, it is not the total amount of 

 nutriment absorbed by the vestiges that is in question, but only 

 the difference in the amounts consumed in the vestigial struc- 

 tures of the individual that survives and the one that perishes. 

 It requires faith of a really magnificent order to believe, for 

 instance, that the daily addition or subtraction of a grain or less 

 of nutriment can have influenced the survival rate of the Greenland 

 whale. 



178. Next, it was asserted that the parts of the individual 

 struggle amongst themselves for nutriment, and the parts most 

 used being most stimulated received more than their share, and as 

 a consequence flourish at the expense of the others, which atrophy. 

 This hypothesis, however, is merely a particular application of the 

 Lamarckian doctrine. 



179. In his hypothesis of Germinal Selection, Weismann has 

 very ingeniously transferred the struggle for nutriment from the 

 individual to the germ-plasm. He supposes that the parts of the 

 individual are represented in the germ-plasm by ' determinants/ 

 which multiply like cells, so that descendant determinants are 

 present in descendant germ-cells. A weak determinant produces 

 a minus (retrogressive) variation. Being weak, it is vanquished 

 in the struggle for food by stonger determinants, and so grows 

 weaker, and transmits its weakness to offspring and descendants. 

 If the part it represents be useful, the individual who has the 

 minus variation tends to perish through Natural Selection, the 

 race being continued by the individuals in which the determinant 

 is stronger, and the part therefore better developed. If it is 

 useless, he tends to survive, and the process of weakening con- 

 tinues with added force in successive generations, till at length the 

 determinant perishes and the part disappears. In brief, Weismana 

 supposes that the determinants of useless parts are not helped by 

 selection, whereas the determinants of useful parts are helped by 

 it ; and, therefore, that the former tend to be vanquished by the 

 latter in the struggle for nutriment. 



1 80. Weismann's hypothesis consists of two portions an 

 induction and a deduction, the latter being an expansion of the 

 former. (a) Mere cessation of selection is followed by retro- 

 gression, (b} because the determinants of useless parts tend to be 

 starved. It is possible to agree with the first, which is founded 

 on observed facts and can be tested, without assenting to the 

 second, which is neither founded on observed facts nor has been 

 tested. According to this hypothesis, lack of nutriment is a cause 



