268 DEFINITE ACTION OF THE Chap. XXIII. 



I have received, this seems likewise to be the case to a certain 

 extent with sheep in Australia. 



Climate definitely influences the hairy covering of animals; in 

 the West Indies a great change is produced in the fleece of sheep, 

 in about three generations. Dr. Falconer states 31 that the Thibet 

 mastiff and goat, when brought down from the Himalaya to 

 Kashmir, lose their fine wool. At Aagora not only goats, but 

 shepherd-dogs and cats, have fine fleecy hair, and Mr. Ainsworth ffl 

 attributes the thickness of the fleece to the severe winters, and its 

 silky lustre to the hot summers. Burnes states positively 33 that the 

 Karakool sheep lose their peculiar black curled fleeces when removed 

 into any other country. Even within the limits of England, I have 

 been assured that the wool of two breeds of sheep was slightly 

 changed by the flocks being pastured in different localities. 34 It 

 has been asserted on good authority 3S that horses kept during 

 several years in the deep coal-mines of Belgium become covered 

 with velvety hair, almost like that on the mole. These cases 

 probably stand in close relation to the natural change of coat in 

 winter and summer. Naked varieties of several domestic animals 

 have occasionally appeared ; but there is no reason to believe that 

 this is in any way related to the nature of the climate to which 

 they have been exposed. 36 



It appears at first sight probable that the increased size, the 

 tendency to fatten, the early maturity and altered forms of our 

 improved cattle, sheep, and pigs, have directly resulted from their 

 abundant supply of food. This is the opinion of many competent 

 judges, and probably is to a great extent true. But as far as form is 

 concerned, we must not overlook the more potent influence of 

 lessened use on the limbs and lungs. We see, moreover, as far as 

 size is concerned, that selection is apparently a more powerful agent 

 than a large supply of food, for we can thus only account for the 

 existence, as remarked to me by Mr. Blyth, of the largest and 

 smallest breeds of sheep in the same country, of Cochin-China fowls 

 and Bantams, of small Tumbler and large Bunt pigeons, all kept 

 together and supplied with abundant nourishment. Nevertheless 

 there can be little doubt that our domesticated animals have been 

 modified, independently of the increased or lessened use of parts, by 

 the conditions to which they have been subjected, without the aid 

 of selection. For instance, Brof. Riitimeyer 3? shows that the bones of 



31 ' Natural History Review,' 1862, 'Hist. Nat. Gen.,' torn. iii. p. 438. 



p. 113. 3e Azara has made some good re- 



32 ' Journal of Roy. Geographical marks on this subject, ' Quadruples 

 Soc.,' vol. ix., 1839, p. 275. du Paraguay,' torn. ii. p. 337. See 



33 'Travels in Bokhara,' vol. iii. p. an account of a family of naked mice 

 151. produced in England, ' Proc. Zoolog. 



34 See also, on the influence of Soc.,' 1856, p. 38. 



marshy pastures on the wool, Godron, 37 ' Die Fauna der Pfahlbauten,' 



'L'Kspece,' torn. ii. p. 22. 1861, s. 15. 

 ** Isidore GeofFroy Saint-Hilaire, 



