238 
SEXUAL selection: birds. 
Part IL 
loured for the sake of protection. In some instances 
the upper exposed surface of the plumage has been thus, 
coloured in both sexes, whilst the lower surface in the 
males alone has been variously ornamented through 
sexual selection. Finally, from the facts given in these 
four chapters, we may conclude that weapons for battle, 
organs for producing sound, ornaments of many kinds, 
bright and conspicuous colours, have generally been 
acquired by the males through variation and sexual 
selection, and have been transmitted in various ways 
according to the several laws of inheritance — the fe- 
males and the young being left comparatively but little 
modified.^^ 
I am greatly indebted to the kindness of Mr. Sclater for having 
looked over these four chapters on birds, and the two following ones 
on mammals. By this means I have been saved from making mistakes 
about the names of the species, and from giving any facts which are 
actually known to this distinguished naturalist to be erroneous. . But 
of course he is not at all answerable for the accuracy of the statements, 
quoted by me from various authorities. 
