4'2 
‘'Redundancy or deficiency of nutriment affects chiefly tlic 
stature of animals. Those herbivorous quadrupeds who browse tlio 
scanty vegetation on mountains are invariably mucli smaller than 
their brethren who crop the luxuriant produce of the plains ; and 
although the cattle usually kept in these different situations are 
0 diverse breeds, yet eitlier of the breeds gradually removed to 
t le other’s pasture, would in two or three generations acquire 
many of the characters of the other ; would increase or degenerate 
in size according to the supply of nutritious food, though in either 
case they would most probably soon give birth to true varieties 
ailapted to the change. 
III. Lreeds are sometimes formed by accident or isolation 
in a state of nature, but are for the most part brought about 
by the direct agency of man. 
“It IS a general law of nature for all creatures to propagate 
the hke of themselves ; and this extends even to the most trivial 
minutue, to the slightest individual peculiarities; and thus 
among ourselves we see a family likeness transmitted from gene- 
ration to generation. When two animals are matched togeUier, 
each remarkable for a certain given peculiarity, no matter how 
trivial, there is a decided tendency in nature for that peculiarity 
to increase. And if the produce of those animals be set apart, 
and only those ni which the same peculiarity is most apparent 
be selected to breed from, the next generation will possess it in 
a still more marked degree, and so on, till at length the variety 
I designate a ‘ breed ’ is formed, Avhich may be very unlike the 
original type. 
“Ihe exanqiles of this class of varieties must be too obvious 
to need specification. Many of the varieties of cattle, and, in 
all probability, the greater number of those of domestic picreons 
have been generally brought about in this manner. It is worthy 
of ^ remarlq however, that the original and typical fonn of an 
animal is in great measure kept up by the same identical means 
by which a true breed is produced. The original form of species 
is unquestionably better adapted to its natural habits than any 
modification of. tliat form ; and as the sexual passions excite 
to rivalry and conflict, and the stronger must always prevail 
over the iveaker, the latter in a state of nature is allowed but 
few opportunities of continuing its race. In a large herd of 
