( 



250 



CHANGES IN ANIMALS AND PLANTS 



[Ch. XXXIV. 



cultivated fields ? Where do we find in nature our cabbages, 

 lettuces, and other culinary vegetables, in the state in which 

 they appear in our gardens ? Is it not the 



same 



animals which domesticity 



or considerably modified ? ' ^ 

 pigeons are unlike any wild birds. 



Our domestic fowls and 



domestic 

 themselv( 



and 



higher regions of the air, and crossing extensive countries in 

 their flight, like the wild ducks and wild geese from which 

 they were originally derived. A bird which we breed in a 

 cage cannot, when restored to liberty, fly like others of the 

 same species which have been always free. This small 

 alteration of circumstances, however, has only diminished 

 the power of flight, without modifying the form of any part 

 of the wings. But when individuals of the same race are 

 retained in captivity during a considerable length of time, 

 the form even of their parts is gradually made to difPer, 

 especially if climate, nourishment, and other circumstances 

 be also altered. 



The numerous races of dogs which we have produced by 

 domesticity are nowhere to be found in a wild state. In 

 nature we should seek in vain for mastiffs, harriers, spaniels, 

 greyhounds, and other races, between which the differences 

 are sometimes so great that they would be readily admitted 

 as specific between wild animals ; ^ yet all these have sprung 

 originally from a single race, at first approaching very near 

 to a wolf, if, indeed, the wolf be not the true type which at 

 some period or other Avas domesticated by man.' 



Although important changes in the nature of the places 

 which they inhabit modify the organisation of animals as 



well as vegetables ; yet the former, says Lamarck, require 

 more time to complete a considerable degree of transmu- 

 tation; and, consequently, we are less sensible of such 

 occurrences. ]N"ext to a diversity of the medium in which 

 animals or plants may live, the circumstances which have 

 most influence in modifying their organs are differences in 

 exposure, climate, the nature of the soil, and other local 

 particulars. These circumstances are as varied as are the 



* Phil. Zool. torn, i. p. 227. 



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