Darwin's Theory of Sexual Selection 195 
more brilliant during the breeding season, and which are 
sedulously displayed before the females. The males also 
endeavor to charm or excite their mates by love-notes, songs, 
and antics; and the courtship is, in many instances, a pro- 
longed affair. Hence it is not probable that the females are 
indifferent to the charms of the opposite sex, or that they are 
invariably compelled to yield to the victorious males.” 
Thus a double process of selection is imagined to take 
place ; one, the outcome of a competition of the males with 
each other, and the other, through a choice of the more suc- 
cessful males by the females, the more beautiful being 
supposed to be chosen. 
It may be well not to lose sight of the fact that unless the 
selection is severe in each generation, its good effects will be 
lost, as has been stated in connection with the theory of nat- 
ural selection. Still more important is the consideration 
that unless the same variations appear at the same time, in 
many of the surviving males, the results will be lost through 
crossing. These statements will show that the difficulties of 
the theory are by no means small, and when we are asked to 
believe further that another process still has been superim- 
posed on this one, namely, the selection of the more beautiful 
males by the females, we can appreciate how great are the 
difficulties that must be overcome in order that the process 
may be carried out. 
The love-antics and dances of male birds at the breeding 
season furnish many curious data. The. phenomena are 
imagined by Darwin to be connected with sexual selection, 
for in the dances the males are supposed to exhibit their or- 
naments to the females who are imagined to choose the suitor 
that is most to their taste. 
Hudson, who has studied the habits of birds in the field, 
asks some very pertinent questions in connection with their 
performances of different kinds. ‘“ What relation that we 
can see or imagine to the passion of love and the business of 
