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Review of Darwin’s Theory on the Origin of Species. 167 
e, still it appears from the readiness with which such varie- 
ties originate, that a certain amount of disturbance would carry 
them beyond the influence of the primordial attraction, where 
ey may become new centres of variation. 
Some suppose that races cannot be perpetuated indefinitely 
even by keeping up the conditions under which they were fixed: 
but the high antiquity of several, and the actual fixity of many 
of them, negative this assumption. “To ass at we could 
not breed our cart and race horses, long and short-horned cattle, 
and poultry of various breeds, for almost an infinite number of 
generations would be opposed to all experience.” 
y varieties develope so readily and deviate so widely un- 
der domestication, while they are apparently so rare or so tran- 
sient in free nature, may easily be shown. In nature, even with 
hermaphrodite plants, there is a vast amount of cross fertilization 
larting from a suggestion of the late Mr. Knight, now so famil- 
lat, that close interbreeding diminishes vigor and fertility+; and 
Peteeiving that bisexuality is ever aimed at in nature,—being at- 
tained hysiologically in numerous cases where it is not structur- 
las - Varwin has worked out the subject in detail, and shown 
W general is the concurrence, either habitual or occasional, of 
and has drawn the philosophical inference that probably no or- 
8 being self-fertilizes indefinitely ; but that a cross with an- 
. oo vidual is occasionally—perhaps at very long inter- 
-.s—indispensable. We refer the reader to the section on the 
wttercrossing of individuals (p. 96-101), and also to an article 
mae Gardeners’ Chronicle a year and a half ago, for the de- 
th of a very interesting contribution to science, irrespective of 
in tt domestication, this intercrossing may be prevented; and 
u's Prevention lies the art of producing varieties. But “the 
— 1s Nature,” since the whole art consists in allowing the 
ita universal of all natural tendencies in organic things (inher- 
tal ) to Operate uncontrolled by other and — on 
0 
into Play ra b nea he stock of a desirable variety so 
Separating the s 0. : 
8 to prevent pikes, or te selecting for breeders those indi- 
— Pct that this is not an ultimate fact, but = natural consequence of in- 
breeding | inheritance of disease or of tendency to disease, which close inter- 
inate © PefPetuates and accumulates, but wide breeding may neutralize or elim- 
= Vol, Pas : 
rh Pee [2], 1854, p. 18, 
