118 OTHER FACTORS OF EVOLUTION 



Dimorphism in the Animal Kingdom,"' but I must confine myself 

 here to a brief account of his own views on this subject, which 

 are strongly expressed, and definitely Lamarckian in character. 



He says {loc. cit. p. 30), "The fundamental objection to Darwin's 

 theory of sexual selection, or any other selection theory, is that 

 it does not account for the origin of the variations which it 

 assumes . . . there are two almost universal peculiarities of 

 secondary sexual characters on which the theory of sexual 

 selection throws no light whatever : (i) the characters do not 

 begin to appear in the individual until it is nearly adult and sexually 

 mature, in other words they appear when, or a little before, 

 the animal begins to breed ; (2) they are inherited only by the sex 

 which possesses them," or, in other words, only by the members 

 of one sex. 



Unisexual characters have, as a general rule, some function 

 or importance in the special habits, or conditions of life, of the 

 sex in which they occur ; whether they are fighting weapons like 

 the antlers of stags ; allurements as in the special plumes of male 

 birds which are erected and displayed in courtship ; or love-notes 

 as in the songs of birds generally. " So far," Cunningham says, 

 " there can be no doubt that Darwin was perfectly right and his 

 opponents all wrong. The facts being so, there is rivalry, combat, 

 and competition. But the important truth which appears to have 

 been generally overlooked, is that in the case of each special 

 organ its special employment subjects it to special, usually 

 mechanical, irritation or stimulation, to which other organs of 

 the body are not subjected." Such constantly repeated irritations 

 or stimulations are causes thoroughly well recognised as being 

 capable of producing physiological effects on the tissues of a 

 distinct kind, and have been much dwelt upon by E. D. Cope 

 in his important work, "The Primary Factors of Organic 

 Evolution." ^ So that, as Cunningham says, " not only hypotheti- 

 cally at some former time, but actually at present in every 

 individual, the unisexual organs or appendages are subjected 

 in their functional activity to special strains, contacts, and 

 pressures, that is, to stimulation, which must and does have 

 some physiological effect on their development and mode of 

 growth." 



It is quite evident that the development of these ' physiological 



» 1900, pp. 24-44. = 1896, Chicago. 



