276 
THE PRINCIPLES OF 
Part II. 
are said to occur. Dr. Burt Wilder 18 lias 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 
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, 
18 ‘Massachusetts Medical Soc.’ vol. ii. No. 3, 1868, p. 9. 
