TRAINING NEEDFUL FOR NATURALISTS. 343 
of natural selection—experience difficulties in arriving at a 
rational understanding of them, which are similar to those 
experienced by the uncivilized tribes of nature when con- 
templating the latest complicated productions of engineer- 
ing. Savages who see a ship of the line, or a locomotive 
engine for the first time, look upon these objects as the 
productions of a supernatural being, and cannot understand 
how a man, an organism like themselves, could have pro- 
duced such an engine. Even the uneducated classes of our 
own race cannot comprehend such an intricate apparatus 
in its actual workings, nor can they understand its purely 
mechanical nature. Most naturalists, however, as Darwin 
very justly remarks, stand in much the same position in 
regard to the forms of organisms as do savages to ships of 
the line and to locomotive engines. A rational understand- 
ing of the purely mechanical origin of organic forms can 
only be acquired by a thorough and general training in 
Biology, and by a special knowledge of comparative 
_anatomy and the history of development. 
Among the remaining objections to the Theory of Descent, 
I shall here finally refer to and refute but one more, as in 
the eyes of many unscientific men it seems to possess great 
weight. How are we, from the Theory of Descent, to conceive 
of the origin of the mental faculties of animals, and more 
especially their specific expressions—the so-called instincts ? 
This difficult subject has been so minutely discussed by 
Darwin in a special chapter of his chief work (the seventh), 
that I must refer the reader to it. We must regard instincts 
as essentially the habits of the soul acquired by adaptation, 
and transmitted and fixed by inheritance through many 
generations. Instincts are, therefore, like all other habits, 
