DARWINISM ATTACKED. 125 



sooner or later developed by heredity, but only in associa- 

 tion with the physiological conditions under which they were 

 originally produced. This is the explanation of the limita- 

 tions of particular modifications not merely to particular 

 species or kinships, but to particular periods in the life of 

 the individual, to a particular sex and even to a particular 

 season of the year in that sex." The author believes that an 

 examination of secondary sexual characters shows that they 

 develop at places and in parts which are at the time of 

 sexual excitement unusually directly stimulated by exertion 

 or contact or use. These secondary sexual characters are 

 "in many cases not merely limited to the period of mature 

 life but actually to that part of the year in which the repro- 

 ductive organs are active, that is to the breeding season." 



In closing this chapter given up to objections to the Dar- 

 winian theories of natural and sexual selection, attention 

 may be called to Wolff's * ' objection to natural 

 Importance of selection based upon the dependence of the na- 



the sexual selec- , , ,. ,, 11,- 



tion theory as a ttiral selection theory on the sexual selection 

 support of the _ theory for explanation of the existence of orna- 



natural selection 



theory. mental characters, and ot all these secondary 



sexual characters, which are useless or even 

 apparently disadvantageous in the life-and-death inter- 

 specific struggle for space and food. As Wolff looks on the 

 sexual selection theory as wholly discredited, he finds this 

 necessary dependence on it by believers in natural selection 

 for the explanation of those characters just mentioned 

 strong evidence for the weakness of the natural selection 

 theory. 



APPENDIX. 



1 Kramer, Paul, "Theorie u. Erfahrung; Beitrage zur Beurtheilung 

 des Darwinismus," 1877, Halle. An interesting paper criticising 

 the selection theories from two points of view ; first, on the basis of 

 a mathematical treatment of the Darwinian hypothesis (especially 

 that of sexual selection), the author taking Darwin's premises and 

 by a mathematical handling of them showing that they do not lead 



