The Zoologist— August, 1867. 843 



Again with horses, the methodical cropping out of hereditary 

 peculiarities is a fact familiar to breeders ; and even such natural 

 peculiarities as the diverse colour of the two eyes are manifestly 

 transmissible, and with almost absolute certainty, in alternate gene- 

 rations.* 



It is, however, only by direct observation, and by the most 

 careful breeding, that the phenomenon of avism can be clearly 

 exemplified. The word " atavism," as rigidly applied, implies a rever- 

 sion to the ancestral peculiarities or characters exhibited prior to 

 grandparents; but avism as we shall find it in insects (which is really 

 the point to be considered) goes back no farther than the penultimate 

 generation : this is abundantly exemplified in horses, horned cattle, 

 dogs, cats, rabbits, guinea-pigs, poultry and pigeons ; and much as it 

 may have been hidden from naturalists, it is perfectly familiar to 

 breeders and dealers, who of course find their advantage in the know- 

 ledge. In guinea-pigs it is considered desirable to get them of two 

 colours only, the ordinary colours being black, white and yellow ; 

 yellow is the colour least in favour, and of course breeders consider it 

 desirable to exclude it altogether; but the sagacious breeder does not 

 destroy the pigs adorned with this colour, unless the parents possessed 

 the same ornamentation, for he knows that if a female possessing the 

 desired character of colour produces tricoloured young, then the . 

 progeny of those young will assuredly revert to the desired colours of 

 the grandmother. I have myself kept guinea-pigs, and have had 

 excellent opportunities of observing this. Knowing the prevailing 

 fashion, for I can call it nothing else, I once purchased a female 

 guinea-pig with a perfectly white body and a perfectly black head : I 

 kept her six years, during which period she of course produced " little 

 pigs galore," but not one inherited the maternal perfections; yet 

 among her grand-children the black heads were so abundant that I 

 could afford to supply all my porcellus-fancying friends with these 

 desirable cavies. In taking leave of these tailless pets, I may say 



* An interesting note on this subject appears in the • Zoologist' for June (S. S. 788), 

 from the pen of Mr. Clark-Kennedy, concerning; a dog which had eyes of different 

 colours. "The man told me," he writes, "the dog was born with one eye blue and 

 one dark brown. His mother was a greyhound and his father a mongrel, and their 

 eyes were of the usual colour; but his grandfather was ' chany-eyed,' ibat is, had one 

 eye blue and one brown. Might not this peculiarity have passed over one generation, 

 in much the same way as lunacy or gout in families?" Certainly it had ; and the 

 comparison is not only to the point, but shows how well this natural law is kuuwu to 

 observers. 



