160 
DARWINISM 
CHAP. 
has received decisive evidence that the hybrids between these 
are perfectly fertile inter se. 
Dogs have been frequently crossed with wolves and with 
jackals, and their hybrid offspring have been found to be fertile 
inter se to the third or fourth generation, and then usually to 
show some signs of sterility or of deterioration. The wolf 
and dog may be originally the same species, but the jackal is 
certainly distinct; and the appearance of infertility or of weak¬ 
ness is probably due to the fact that, in almost all these experi¬ 
ments, the offspring of a single pair—themselves usually from 
the same litter—were bred in-and-in, and this alone sometimes 
produces the most deleterious effects. Thus, Mr. Low in his 
great work on the Domesticated Animals of Great Britain , 
says : “ If we shall breed a pair of dogs from the same litter, 
and unite again the offspring of this pair, we shall produce at 
once a feeble race of creatures ; and the process being repeated 
for one or two generations more, the family will die out, or be 
incapable of propagating their race. A gentleman of Scotland 
made the experiment on a large scale with certain foxhounds, 
and he found that the race actually became monstrous 
and perished utterly.” The same writer tells us that hogs 
have been made the subject of similar experiments : “After a 
few generations the victims manifest the change induced in the 
system. They become of diminished size; the bristles are 
changed into hairs; the limbs become feeble and short ; the 
litters diminish in frequency, and in the number of the young 
produced ; the mother becomes unable to nourish them, and, 
if the experiment be carried as far as the case will allow, the 
feeble, and frequently monstrous offspring, will be incapable of 
being reared up, and the miserable race will utterly perish.” 1 
These precise statements, by one of the greatest authorities 
on our domesticated animals, are sufficient to show that the 
fact of infertility or degeneracy appearing in the offspring of 
hybrids after a few generations need not be imputed to the 
fact of the first parents being distinct species, since exactly the 
same phenomena appear when individuals of the same species 
are bred under similar adverse conditions. But in almost all 
the experiments that have hitherto been made in crossing 
distinct species, no care has been taken to avoid close inter- 
1 Low’s Domesticated Animals of Great Britain, Introduction, p. lxiv. 
