276 THE PRINCIPLES OF Part II. 



are said to occur. Dr. Burt Wilder 18 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 that women would 

 more frequently endeavour to conceal a deformity of 

 this kind than men. Whether the large proportional 

 number of deaths of the male offspring of man and 

 apparently of sheep, compared with the female offspring, 

 before, during, and shortly after birth (see supplement), 

 has any relation to a stronger tendency in the organs 

 of the male to vary and thus to become abnormal in 

 structure or function, I will not pretend to conjecture. 



In various classes of animals a few exceptional cases 

 occur, in which the female instead of the male has 

 acquired well pronounced secondary sexual characters, 

 such as brighter colours, greater size, strength, or pug- 

 nacity. With birds, as we shall hereafter see, there 

 has sometimes been a complete transposition of the 

 ordinary characters proper to each sex ; the females 

 having become the more eager in courtship, the males 

 remaining comparatively passive, but apparently select- 

 ing, as we may infer from the results, the more attractive 

 females. Certain female birds have thus been rendered 

 more highly coloured or otherwise ornamented, as well 

 as more powerful and pugnacious than the males, these 

 characters being transmitted to the female offspring 

 alone. 



It may be suggested that in some cases a double 



J DO 



process of selection has been carried on ; the males 

 having selected the more attractive females, and the 

 latter the more attractive males. This process however, 

 though it might lead to the modification of both sexes, 



13 'Massachusetts Medical Soc' vol. ii. No. 8, 1868, p. 9. 



