334 LAWS OF VAEIATION. Chap. XXV. 



changes of structure would have been indispensable, — namely, 

 a thickened skull to carry the horns; strengthened cervical 

 vertebrae, with strengthened ligaments ; enlarged dorsal verte- 

 brae to support the neck, with powerful fore-legs and feet ; all 

 these parts being supplied with proper muscles, blood-vessels, 

 and nerves. How then could these admirably co-ordinated 

 modifications of structure have been acquired? According to 

 the doctrine which I maintain, the horns of the male elk were 

 slowly gained through sexual selection, — that is, by the best- 

 armed males conquering the worse-armed, and leaving a greater 

 number of descendants. But it is not at all necessary that 

 the several parts of the body should have simultaneously varied. 

 Each stag presents individual differences, and in the same 

 district those which had slightly heavier horns, or stronger 

 necks, or stronger bodies, or were the most courageous, would 

 secure the greater number of does, and consequently leave a 

 greater number of offspring. The offspring would inherit, in 

 a greater or less degree, these same qualities, would occasionally 

 intercross with each other, or with other individuals varying in 

 some favourable manner; and of their offspring, those which 

 were the best endowed in any respect would continue multi- 

 plying; and so onwards, always progressing, sometimes in one 

 direction, and sometimes in another, towards the present excel- 

 lently co-ordinated structure of the male elk. To make this 

 clear, let us reflect on the probable steps, as shown in the 

 twentieth chapter, by which our race and dray-horses have 

 arrived at their present state of excellence ; if we could view the 

 whole series of intermediate forms between one of these animals 

 and an early unimproved progenitor, we should behold a vast 

 number of animals, not equally improved in each generation 

 throughout their entire structure, but sometimes a little more 

 in one point, and sometimes in another, yet on the whole gradu- 

 ally approaching in character to our present race or dray- 

 horses, which are so admirably fitted in the one case for fleetness 

 and in the other for draught. 



Although natural selection would thus 33 tend to give to the 



33 Mr. Herbert Spencer ('Principles remarks: "We have seen reason to 

 of Biology,' 1864, vol. i. pp. 452, 46S) " think that, as fast as essential faculties 

 takes a different view ; and in one place " multiply, and as fast as the number of 





