DAR^VmiSJI CHAP. 



two years the sparrows began to attack them, and thereafter 

 destroyed them quite as readily as the yellow ones ; and he 

 believes it was merely because some bolder sparrow than the 

 rest set the example. On this subject Mr. Charles C. Abbott 

 well remarks : " In studying the habits of our American birds 

 — and I suppose it is true of birds everywhere — it must at all 

 times be remembered that there is less stability in the habits 

 of birds than is usually supposed ; and no account of the habits 

 of any one species "will exactly detail the various features of 

 its habits as they really are, in every portion of the terri- 

 tory it inhabits." ^ 



Mr. Charles Dixon has recorded a remarkable change in the 

 mode of nest-building of some common chaffinches which were 

 taken to New Zealand and turned out there. He says : " The 

 cup of the nest is small, loosely put together, apparently lined 

 with feathers, and the walls of the structure are prolonged for 

 about 18 inches, and hang loosely down the side of the 

 supporting branch. The whole structure bears some re- 

 semblance to the nests of the hangnests (Icteridre), "with the 

 exception that the cavity is at the top. Clearly these N^ew 

 Zealand chaffinches were at a loss for a design when fabricat- 

 ing their nest. They had no standard to Avork by, no nests of 

 their own kind to copy, no older birds to give them any instruc- 

 tion, and the result is the abnormal structiu'e I have just 

 described."^ 



These few examples are sufficient to show that both the 

 habits and instincts of animals are subject to variation ; and 

 had we a sufficient number of detailed observations we should 

 probably find that these variations were as numerous, as 

 diverse in character, as large in amount, and as independent 

 of each other as those which we have seen to characterise 

 their bodily structui'e. 



The Variability of Plants. 



The variability of plants is notorious, being proved not only 

 by the endless variations which occur whenever a species is 

 largely grown by horticulturists, but also by the great difficulty 

 that is felt by botanists in determining the limits of species in 



^ Nature, vol. xvi. p. 163 ; and vol. xi. p. 227. 

 " Ihid., vol. xxxi. (1SS5), p. 533. 



