304 



LAWS OF VARIATION. 



Chap. XXIV. 



CP 



a Chinese sow by a wild Alpine boar ; they lived free in the 

 park, and were so tame that they came to the house to he 

 fed ; but they would not touch swill, which was devoured by 

 the other pigs. An animal when once accustomed to an 



un- 



natural diet, which can generally be effected only during youth 

 dislikes its proper food, as Spallanzani found to be the 



case 



with a pigeon which had been long fed on meat. Individuals 

 of the same species take to new food with different degrees of 

 readiness; one horse, it is stated, soon learned to eat meat, 

 whilst another would have perished from hunger rather than 

 have partaken of it. 37 



The caterpillars of the Bowhyx hesperus feed in a state of 

 nature on the leaves of the Cafe diable, but, after having been 

 reared on the Ailanthus, they would not touch the Cafe diable, 

 and actually died of hunger. 



It has been found possible to accustom marine fish to live 

 in fresh water ; but as such changes in fish, and other marine 

 animals, have been chiefly observed in a state of nature, they 



38 



do 



not properly belong 



to our present subject. The period 

 of gestation and of maturity, as shown in the earlier chapters, 

 the season and the frequency of the act of breeding, — have all 

 been greatly modified under domestication. With the Egyptian 



'oose the rate of change in the season has been recorded. 39 



The wild drake pairs with one female, the domestic drake is 



polygamous. 



Certain breeds of fowls have lost the habit of 



incubation. The paces of the horse, and the manner of flight 

 in certain breeds of the pigeon, have been modified, and are 

 inherited. The voice differs much in certain fowls and pigeons. 

 Some breeds are clamorous and others silent, as in the Call and 

 common duck, or in the Spitz and pointer dog. Every one 

 knows how dogs differ from each other in their manner of 

 hunting, and in their ardour after different kinds of game or 



vermin. 



With plants the period of vegetation is easily changed and 

 is inherited, as in the case of summer and winter wheat, barley, 



563. 



3 7 This and several other cases are Soc. d'Acclimat.,' torn, viii., 1861, p 

 given by Colin, ' Physiologie Comp. des 

 Animaux Com.,' 1854, tom. i. p. 426. 39 Quatrefages, ' Unite de l'Espece 



38 M. Michely de Cayenne, in ' Bull. "Surname,' 1861, p. 79. 



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