GENERAL PRINCIPLES OF BREEDING. 69 



dark brown color, with red legs, bore two litters of puppies 

 to a mongrel cur, all of which were colored like the sire 

 black, with red legs and white feet. On the third occasion 

 she was lined by a pure Skye terrier, of a grey color; and, 

 to avoid accidents, was locked up with this dog during the 

 whole continuance of the heat. The issue was two puppies 

 closely resembling the mongrel cur in color, shape and gen- 

 eral appearance. Instances of the same kind have fallen 

 under the observation of almost every dog-fancier. 



Many have sought to explain the phenomenon as a simple 

 result of the strong impression made upon the mind of the 

 dam by the sire of her earlier offspring; and, doubtless, this 

 may sometimes co-operate, but is altogether inadequate to 

 account for the frequency of the occurrence. The imagina- 

 tion affects the progeny of a very limited number of females, 

 whereas the phenomenon we are considering among the 

 domestic quadrupeds is the rule rather than the exception, 

 so that a more satisfactory cause must be sought for. 



McGillivray advances the theory that the elements from 

 the blood of the foetus, absorbed into that of the mother, 

 contaminate her blood, and reduce her to a cross, thus render- 

 ing her forever after incapable of producing a pure-bred off- 

 springi Not that he supposes the blood of the foetus, as 

 such, to circulate within the veins of the mother, but that 

 fine particles from the blood of the offspring pass through 

 the intervening layers of cells, and thus reach the maternal 

 blood and reproduce themselves there. But the whole the- 

 ory is an assumption. We know that the placenta, or after- 

 birth, by which the foetus is connected to the mother, 

 serves the purposes of both stomach and lungs. From the 

 glands in the walls of the womb a milk-like liquid is con- 

 stantly secreted, which, being absorbed by the foetal vessels 

 branching in the placenta, is carried into the blood of the 

 young animal and serves to nourish it, just as the milk from 

 the udder does after birth. Again, from the blood of the 

 offspring circulating in the placenta carbonic acid is given 

 off and taken into the maternal blood, while oxygen supplied 

 by the blood of the dam is taken up by the blood of the foetus. 

 So far these membranes fulfill the functions of stomach and 



