the Varieties of Animals. 43 



breeds are in a state of nature so rarely perpetuated. There 

 is yet, however, before quitting this subject, another sort of 

 albino to be considered, which, I believe, is peculiar to the 

 feathered race, and which is not, like the others, permanent; 

 these, therefore, I shall denominate temporary albinoes. Most 

 of the pale, white, and pied varieties of birds, which are pro- 

 duced in a state of nature, are of this kind. A friend informs 

 me that a perfectly white lark in his possession moulted, and 

 became of the ordinary hue. I lately shot a sparrow which 

 was all over of a very pale brown, or cream colour ; it was 

 moulting, and some of the new feathers that were coming 

 were of the usual colour, and others were of a pure white : 

 on the next moult, probably, no more white feathers would 

 have appeared. Of a brood of young robins which frequented 

 my garden, two were white, one partially so, and one of the 

 usual mottled brown ; these all moulted into the ordinary 

 colour. I could add other instances to the list, especially 

 amongst domestic poultry. But it does not hence follow 

 that among wild birds there are no permanently white or pied 

 varieties ; or, in other words, no true partial and semi-albi- 

 noes. A blackbird with a white head has now inhabited a 

 garden in this neighbourhood for three successive years ; and 

 if the cupidity of collectors did not mark out every white or 

 pied bird for destruction, I doubt not that I should have 

 been able to have furnished some other similar instances of 

 •permanent variation. 



II. Acquired Variations. — The second class of varieties 

 which I would designate thus, comprises the various changes 

 which, in a single individual, or in the course of generations, 

 are gradually brought about by the operation of known 

 causes : such as the greater or less supply of fiutriment ; the 

 influence of particular sorts of food ; or, either of these 

 combined with the various privations consequent upon con- 

 finement ; which changes would as gradually and certainly 

 disappear if these causes were removed. 



Redundance or deficiency of nutriment affects chiefly the 

 stature of animals. Those herbivorous quadrupeds which 

 browse the scanty vegetation on mountains are invariably 

 much smaller than their brethren which crop the luxuriant 

 produce of the plains ; and although the cattle usually kept 

 in these different situations are of diverse breeds ; yet either 

 of the breeds gradually removed to the other's pasture, 

 would, in two or three generations, acquire many of the cha- 

 racters of the other, would increase or degenerate in size, 

 according to the supply of nutritious food ; though, in either 

 case, they would most probably soon give birth to true va- 

 rieties adapted to the change. In this instance, temperature 



