DARWIN'S VARIOUS WORKS. 137 
nomena of organic nature, which agree in bearing testimony 
to the truth of the Theory of Selection. 
Darwin, at first, intentionally did not notice the important 
conclusion from his Theory of Descent, namely, the descent 
of the human race from other mammals. It was not till 
this highly important conclusion had been definitely estab- 
lished by other naturalists as the necessary sequel of the 
doctrine of descent, that Darwin himself expressly endorsed 
it, and thereby completed his system. This was done in 
the highly interesting work, “The Descent of Man, and 
Sexual Selection,’ which appeared as late as 1871, and has 
likewise been translated into German by Victor Carus.® 
The careful study which Darwin devoted to domestic 
animals and cultivated plants was of the greatest import- 
ance in establishing the Theory of Selection. The infinitely 
varied changes of form which man has produced in these 
domesticated organisms by artificial selection are of the 
very highest importance for a right understanding of animal 
and vegetable forms; and yet this study has, down to the 
most recent times, been most grossly neglected by zoologists 
and botanists. Without entering upon the discussion of the 
significance to be attached to the idea of species itself, they 
have filled not only bulky volumes, but whole libraries, 
with descriptions of individual species, and with most 
childish controversies as to whether these species are good, 
or tolerably good, and bad, or tolerably bad. If naturalists 
instead of spending their time on these useless fancies had 
duly studied cultivated organisms, and had examined the 
transmutation of the living forms, instead of the individual 
‘dead ones, they would not have been led captive so long by 
the fetters of Cuvier’s dogma. But as cultivated organisms 
