266 THE BOOK OF A NATURALIST 
excepting that of the sexes; while others are 
gregarious or social, and able to form attach- 
ments not only among themselves, but also with 
those of other species, and, when domesticated, 
with man. There is a third matter, which is doubt- 
less the most important of all, to be considered 
when weighing the comparative advantages of 
different kinds, namely, the habits, or instincts, 
which change so slowly that they are practically 
immutable, even in altered conditions, and which, 
in the domesticated or pet animal, according to 
their character, may prove a source of pleasure and 
profit to man, or, on the contrary, a perpetual 
annoyance and trouble. When our progenitors far 
back in time tamed the animals we now possess, it 
cannot be supposed that they expended much 
thought on such considerations as these: probably 
chance determined everything for them, and they 
took and tamed the animals which came first to 
hand, or which promised to be most useful to them, 
either as food or in assisting them to procure food. 
If they were barbarians they would think little of 
beauty, little of the small differences in intelligence, 
and of the much greater differences in disposition, 
and, naturally, nothing at all about certain instincts 
in some animals which would become increasingly 
repugnant to man in a civilised state. 
We have the dog so constantly with us; the 
grand result of centuries of artificial selection and 
training is so patent to every one, that we have 
actually come to look on this animal as by nature 
