animals of these tribes together under circumstances most
favourable to their intercourse, without any such result, which
in these instances at least was obviously prevented by nothing
else than a mutual repugnance.* The existence of this aversion
was so apparent as to cause the Count, .de Buffon to
doubt-for a time, though he afterwards found reason [for
changing his opinion, the truth of Aristotle’s assertion,, that
dogs, wolves* and foxes will sometimes breed together, I
But in the second place, when animals of different species
have been broughkto; cohabit, it appears that in many
instahces^no offspringis prodiffqf^: and that when conceived
it is not so regularly brought to' perfection as the progeny,
unadulterated, of oahe species. Many such births are prevented
by abortion. : In many conception never takes place
at all, though all the preliminary conditions appear to have
been fulfilled.f
Lastly, the permanent distinction of tribes i^furtherJsecured
by the sterility of hybrid productions.
We have seen that occasional exceptions are known to this
general fa c t; but these though curious and remarkable}assi!so-
lated phenomena, are not of such a. description as to- indicate
any real infringement of the law of nature which maintains
the diversity of tribes in the organized world, Hybrid animals
have never been known to propagate their kind y that is,
by cohabiting with other hybrids of an opposite sex to engender
an offspring similar to themselves. It has been ofily
when coupled with animals of a pure breed that hybrids have
been known to produce at all. Mules have been found
capable of bearing an offspring begotten by horses, but there
is no instance upon record -in which two mules have been
known to breed together. A similar observation holds good
with respect to the hybrid animal generated Jbetween the dog
and the wolf, and to that between the dog and the jackal.
This latter animal has-been found capable of breeding with a
* Buffon Hist. Nat. du Chien. I beg die reader who doubts the-reality of this
supposed natural repugnance to read Buffon’s account of his experiments.
f See the account of an experiment in which no conception took place after a
full and sufficient trial between a male fox and a terrier bitch, of which the details
are given in Dr. Baron’s Life of Dr. Jenner, p. 74.
• dog, but it has never been ascertained that two such hybrid
■creatures could bre<sd_ together. Human care and interference
are perpetually necessary in order to originate and maintain
the existence of such breeds.* Without this interference they
would never have existed, and when called into existence
would speedily disappear.^
In the vegetable kingdom, it is well known that hybrids
produced by cultivation are sometimes capable of bearing
seed, though in a great many instances they are completely
sterile. The extreme'rarity of hybrid plants observed
iff a state of nature, and the difficulty which is
experienced in preserving theiff in gardens afford, as M.
De Candolle has observed, strong reasons for believing that-
-even in the case óf ^prolific hybrids, ifêfundation is difficult
and incompiite; The impediments .opposed by nature to the
fecundation of hybrid plants are referred by M. De Candolle
to severakdifferent principles. He conjectures that the pollen
of hybrid anthers, is'wholly or partially deficient in granule's,;
and that on this difference dépends the absolute sterility of
some, and the comparative, though still defective, fectindity
of other hybrid plants'^ With this supposed defect, he compares
the fact “ que lès mulets’stériles d’animaux sont privés
d ’animalcules?’ That some cause ‘ of this description must
Hiifluencé the results of experiments would appear evident
from the observations of M. Gærtner, who found that the
’SrïUMbér of grîtitis fertilized in each fruit is much less in the
’attempts to produce hybrid fecundation than in the natural
.process. ' It conjectured also by M. De Candolle, that
abortion of the germs or some monstrosity in the organs of
fructification are among the causes which impede the reproduction
of hybrid flowers. It appears, however, that in some
instances these hybrid plants can be made to reproduce,
either by blending them with the primitive kinds, or with
* It is said that female mules in Arabia being pregnant by horses often perish in
giving birth to their young, but that the Arabs are accustomed to preserve the foals
as well as their dams by the Caesarean section. “ Lettere suil’ India Orientale.”
Rudolphi, Beytraege,—ubi supra.
See some excellent observations dû this subject in Mr. Lyells Principles of
Geology, book iii. „
L