Chap. VIII. Sexual Selection. 223 



animals, the females alone are fixed, and the males of these must 

 be the seekers. But it is difficult to understand why the males of 

 species, of which the progenitors were primordially free, should 

 invariably have acquired the habit of approaching the females, 

 instead of being approached by them. But in all cases, in order 

 that the males should seek efficiently, it would be necessary that 

 they should be endowed with strong passions ; and the acquire- 

 ment of such passions would naturally follow from the more 

 eager leaving a larger number of offspring than the less eager. 



The great eagerness of the males has thus indirectly led to their 

 much more frequently developing secondary sexual characters 

 than the females. But the development of such characters 

 would be much aided, if the males were more liable to vary than 

 the females — as I concluded they were — after a long study of 

 domesticated animals. Von Nathusius, who has had very wide 

 experience, is strongly of the same opinion. 22 Good evidence also 

 in favour of this conclusion can be produced by a comparison 

 of the two sexes in mankind. During the Novara Expedition 23 

 a vast number of measurements was made of various parts of the 

 body in different races, and the men were found in almost every 

 case to present a greater range of variation than the women ; but I 

 shall have to recur to this subject in a future chapter. Mr. J. 

 Wood, 24 who has carefully attended to the variation of the muscles 

 in man, puts in italics the conclusion that " the greatest number of 

 '' abnormalities in each subject is found in the males." He had 

 previously remarked that "altogether in 102 subjects, the varieties 

 " of redundancy were found to be half as many again as in 

 " females, contrasting widely with the greater frequency oi 

 " deficiency in females before described." Professor Macalister 

 likewise remarks 25 that variations in the muscles " are probably 

 " more common in males than females." Certain muscles which 

 are not normally present in mankind are also more frequently 

 developed in the male than in the female sex, although exceptions 

 to this rule are said to occur. Dr. Burt Wilder 26 has tabulated 

 the cases of 152 individuals with supernumerary digits, of which 

 86 were males, and 39, or less than half, females, the remaining 

 27 being of unKnown sex. It should not, however, be overlooked 



22 ' Vortrage iiber Viehzucht,' my ' Variation of Animals and 

 1872, p. Go. Plants under Domestication,' vol, ii. 



23 'Keise der Novara: Anthro- 1868, p. 75. 



polog. Theil,' 1867, s. 216-209. 24 'Proceedings Royal Soc' vol. 



The results were calculated by Dr. xvi. July 1868, pp. 519 and 524-. 



Weisbach from measurements made 25 ' Proc. Royal Irish Academy,' 



by Drs. K. Scherzer and Schwarz. vol. s. 1868, p. 123. 



On the greater variability of the 26 'Massachusetts Medical Soc' 



KTAles cf domesticated animils. -=oe vol. ii. Na. 3, l r '6 8 , p. 9. 



