318 Evolution and Adaptation 



differ conspicuously from the common peacock in the color 

 of their secondary wing-feathers, scapulars, wing-coverts, and 

 thighs, and are, I think, more beautiful; they are rather 

 smaller than the common sort, and are always beaten by 

 them in their battles, as I hear from the Hon. A. S. G. Can- 

 ning. The females are much paler-colored than those of 

 the common kind. Both sexes, as Mr. Canning informs me, 

 are white when they leave the egg, and they differ from the 

 young of the white variety only in having a peculiar pinkish 

 tinge on their wings. These japanned birds, though appear- 

 ing suddenly in flocks of the common kind, propagate their 

 kind quite truly." 



In two cases, in which these birds had appeared quite sud- 

 denly in flocks of the ordinary kind, it is recorded that 

 " though a smaller and weaker bird, it increased to the ex- 

 tinction of the previously existing breed." Here we have 

 certainly a remarkable case of a new species suddenly 

 appearing and replacing the ordinary form, although the 

 birds are smaller, and are beaten in their battles. 



Darwin has given an admirably clear statement of his 

 opinion as to the causes of variability in the opening para- 

 graph of his chapter dealing with this topic in his " Animals 

 and Plants." Some authors, he says, " look at variability as a 

 necessary contingent on reproduction, and as much an original 

 law as growth or inheritance. Others have of late encouraged, 

 perhaps unintentionally, this view by speaking of inheritance 

 and variability as equal and antagonistic principles. Pallas 

 maintained, and he has had some followers, that variability 

 depends exclusively on the crossing of primordially distinct 

 forms. Other authors attribute variability to an excess of 

 food, and with animals, to an excess relatively to the amount 

 of exercise taken, or again, to the effects of a more genial 

 climate. That these causes are all effective is highly probable. 

 But we must, I think, take a broader view, and conclude that 

 organic beings, when subjected during several generations to 



