300 
subject, these causes are wholly insufficient, how- 
ever long we may suppose them to operate, to 
change the entire forms of animals, their propor- 
tions, and even their internal structure, to such 
a degree as this hypothesis would require. We 
see that those domestic animals which man has 
transported to the most opposite climates, have 
only changed the quality of their hair or their 
colour. The influence of pasture can only alter 
the height, the proportion of the horns, or per- 
haps add some lumps of fat to the body. Buta 
small number of generations spent on another 
soil are sufficient to overturn whatever this race 
may have acquired during ages of cultivation. 
Again, if we consider those species, whether 
mammalia or birds, which are most populous in 
individuals, and at the same time the most fer- 
tile, the entire of their observed variations are 
by no means great. Some species which are 
very populous are nearly exempt from varieties, 
while others, though less fertile, vary much. 
Thus the common mouse and the mulot, Mus 
sylvaticus, are perhaps as populous as any species ; 
yet their variations are rare ;—and an infinite 
number of instances might be brought forward 
among the fishes and insects. There are even 
species very nearly allied to each other, and al- 
most equally distributed in opposite climates, of 
which the one has run into a great number of 
varieties, while the others every where preserve 
a uniform resemblance to each other. The Polish 
marmot, Arctomys bobac, and the Siberian mar- 
mot, Spermophitus citillus, are striking instances 
that a vegetable diet does not give rise to greater 
varieties than animal food. The Polish marmot 
lives only on vegetables without ever touching 
animal substances, yet it remains unvaried, ac- 
cording to Pallas, from Poland to the banks of 
the Lena. On the contrary, the Siberian mar- 
mot, which is as carnivorous as the surmulot, 
Mus decumanus, has undergone many important 
variations of size, colour, and proportion in the 
same latitudes, and under similar circumstances, 
Although the influence of Domesricarion [see 
that article] has a much more powerful tendency 
to occasion variation, than all those reverses and 
changes which the wild species can experience, 
yet man has not succeeded in altering the nature 
of any one of these animals, so as to form a new, 
distinct, and permanent species. The horse and 
the ass, in their transitions from the wild to the 
domesticated state, have undergone less varia- 
tion than some other wild species, which climate 
alone has been sufficient to modify. The Bac- 
trian camel and the dromedary retain their na- 
tural forms in the few countries where they are 
naturalized. Buffon considered the humps of 
the camel to have been occasioned by the long 
habit of carrying burdens; but the wild camels 
of Thibet and China have the same humps and 
callosities as their domesticated brethren. Pallas 
has correctly observed, that he might as well 
have regarded the follicule of the musk, and the 
SPECIES. 
dorsal gland of the peccari, as abscesses arising 
from disease. The ass is more harshly treated 
than the camel, the alpacas are as much accus- 
tomed to carry burdens, yet they are without 
humps. The horse and the ass have not acquired 
callosities on those places where they have so 
long been exposed to the friction of the saddle 
and harness. 
Climate and food, however long we may sup- | 
pose these causes to operate, are wholly unable 
to account for the existence of the numerous 
species of animals which cover the face of the 
globe. We see that the preservation of the races 
among our domestic animals, and the improve- 
ment of the breeds, depend chiefly upon the 
peculiarities of the individuals selected to propa- 
gate. Graziers have long since laid down those 
rules by which the domestic animals, and espe- 
cially the horse, can be rendered larger, more 
beautiful, or more vigorous than they would have 
been if left uncultivated. But it is only by con- 
tinued care that the purity of the breeds can be 
preserved, and they ever exhibit an inclination 
to resume the characters of the wild animals. 
We thus see that the tendency of the offspring 
to retain the characteristics of its parent is 
powerful enough to counteract all those causes 
which may modify the external forms of animals. 
Thus the introduction of rams of a good breed 
corrects the fleeces of the worst flocks in a single 
generation, and even in the least favourable cli- 
mates. The Angora goat has imparted his silky 
fleece to the Swedish flocks, and they maintain 
this character for several generations. In Russia 
also, the stallions with a frizzled and crisp hair, 
impart to their foals a similar coat and of the 
same colour. The wild, as well as domestic ani- 
mals, also tend continually to maintain their 
primitive forms in opposition to all the influences 
of climate and food, which are wholly insufficient 
to induce this supposed degeneration and degra- 
dation of species. Whenever some accidental 
connate deformity or partial excrescence becomes 
hereditary, as sometimes happens, the natural 
liberty of intercourse soon re-establishes the 
original form ; and it is only by interfering with 
their unions that we can succeed in rendering 
permanent the accidental varieties of our do- 
mestic animals. In the wild state also, the 
females are led instinctively to prefer the most 
courageous of the males, the most perfect, and 
the most masculine of their species. The males, 
likewise, instinctively prefer the most beautiful 
of the females; and thus they both tend to trans- 
mit to their offspring the most perfect form of | 
their species. See the article Brerpine. 
Since Nature then has placed an instinctive 
mutual aversion in animals of different species, 
—since she has rendered hybrids either sterile or 
weak and imperfect,—if allied animals distri- 
buted in remote parts of the globe are found to 
be incapable of yielding fertile races, we have 
presumptive evidence that this supposed degen- 
