29 G LAWS OF VARIATION. Chap. XXIV. 



northern breeds are specifically distinct from the native dogs 

 which flourish in India. The same remark may be made with 

 respect to different breeds of sheep, of which, according to 

 Youatt, 45 not one brought " from a torrid climate lasts out 

 " the second year," in the Zoological Gardens. But sheep 

 are capable of some degree of acclimatisation, for Merino sheep 

 bred at the Cape of Good Hope have been found far better 

 adapted for India than those imported from England. 46 It is 

 almost certain that all the breeds of the fowl are descended 

 from one species ; but the Spanish breed, which there is good 

 reason to believe originated near the Mediterranean, 47 though 

 so tine and vigorous in England, suffers more from frost than 

 any other breed. The Arrindy silk moth introduced from 

 Bengal, and the Ailanthus moth from the temperate province 

 of Shan Tung, in China, belong to the same species, as we 

 may infer from their identity in the caterpillar, cocoon, and 

 mature states ; 48 yet they differ much in constitution : the 

 Indian form " will nourish only in warm latitudes," the other 

 is quite hardy and withstands cold and rain. 



Plants are more strictly adapted to climate than are animals. The 

 latter when domesticated withstand such great diversities of climate, 

 that we find nearly the same species in tropical and temperate 

 countries ; whilst the cultivated plants are widely dissimilar. Hence 

 a larger field is open for inquiry in regard to the acclimatisation of 

 plants than of animals. It is no exaggeration to say that with almost 

 every plant which has long been cultivated, varieties exist which 

 are endowed with constitutions fitted for very different ciimates ; I 

 will select only a few of the more striking cases, as it would be 

 tedious to give all. In North America numerous fruit-trees have 

 been raised, and in horticultural publications, — for instance, in that 

 by Downing, — lists are given of the varieties which are best able to 

 withstand the severe climate of the northern States and Canada. 

 Many American varieties of the pear, plum, and peach are excellent 

 in their own country, but until recently, hardly one was known that 

 succeeded in England; and with apples, 49 not one succeeds. Though 

 the American varieties can withstand a severer winter than ours, the 



45 Youatt on Sheep, 1838, p. 491. municated to Bot. Soc. of Canada, 



16 Royle, 'Prod. Resources of India,' quoted in the 'Reader,' 1863, Nov 



p. lo3. 13th. 



47 Tegetmeier, ' Poultry Book,' 4fl See remarks bv Editor in ' (lard 

 1866, p. 102. Chronicle,' 1848, p. 5. 



48 Dr. II. Paterson, in a paper com- 



