BIOLOGICAL EVOLUTION 67 



It is noteworthy in this connection that Darwin and Wallace 

 had diametrically opposite theories as to the cause of the more 

 brilliant plumage of male birds. "According to Darwin, the 

 gayness of male birds is due to selection on the part of the 

 females; according to Wallace, the soberness of female birds is 

 due to natural selection, which has eliminated those which per- 

 sisted to the death in being gay." * 



Heredity. The fifth and last link to be considered does not 

 yield to Darwin added fame. A follower of Lamarck in the belief 

 that acquired characters were inherited, he was led to make use of 

 this refuge when hard pressed by his opponents. His construc- 

 tive theory, that of pangenesis, — given to the world against 

 the advice of Huxley, 2 — was so completely disproved by Weis- 

 mann as to receive scant reference today, though here, too, he was 

 a prophet and the hope expressed to Sir Joseph Hooker has been 

 fulfilled: " I feel sure that if pangenesis is stillborn it will, thank 

 God, at some future time reappear, begotten by some other father 

 and christened by some other name." 3 Cytology has taken up 

 his task and some who have received his mantle are striving 

 earnestly to discover the secret hidden from his, and up to the 

 present, from all human eyes, — the mystery of heredity. De 

 Vries has made some use of Darwin's hypothesis in his theory of 

 " intracellular pangenesis," so too Weismann in his theory of 

 " determinants," but laboratory experiments have not as yet 

 added conviction to assumption. 



The transmission of acquired characters in the sense used by 

 Lamarck, Spencer and Darwin has been all but disproven, 

 though as we shall see later there is proof of the influence of 

 ontogenetic variations on the offspring, and some ground for 

 believing that habit and environment may furnish conditions 

 favorable for modification of the germ plasm. 



In concluding our discussion of Darwin and the bearing of his 

 theory of natural selection on the problem of this study, first place 

 must be given to the new spirit infused into biological and social 

 science by the publication of his Origin of Species. With 



1 The Evolution of Sex, Geddes and Thomson, p. 10; Wallace, Darwinism, pp. 

 274 f. Cf Morgan, cited above pp. 213 S. 



2 Cf. Fifty Years of Darwinism, p. 93. * Hid., p. 94, 



