54 LEAVES FROM MY NOTE-BOOK. 



authenticated cases have occurred in Great Britain of japanned 

 birds having suddenly appeared, within recent times, in flocks of 

 the common peacock. Mr. Sclater, a high authority, imagined 

 that these black peacocks were a reversion to some breed which 

 would hereafter be discovered in a wild state; but as no wild birds 

 of this description have ever been found, we may consider these 

 japanned peacocks demonstrate one of nature's ways of producing 

 a new species.* 



The constitutional strength of the young japanned peacocks, 

 which led to the extinction of the lighter varieties, is parallelled in 

 many other instances by the increased constitutional strength of 

 many other dark animals. Professor Wyman informed Darwin 

 that " being surprised to find all the Pigs in one part of Virginia 

 black, he made enquiries, and ascertained that these animals fed 

 on the roots of the Lach?iant/ies tinctoria, which colours their 

 bones pink, and, excepting in the case of the black varieties, causes 

 their hoofs to drop off." The squatters therefore chose only black 

 pigs out of a litter for raising, as they alone had a good chance of 

 living. In the Tarentino the inhabitants keep black sheep alone, 

 because the Hypericum crispum abounds there, and this plant does 

 not injure black sheep, but kills the white ones in about a fort- 

 night's time. And similar deep constitutional differences, with 

 regard to susceptibility to certain diseases, is found in the dark and 

 light varieties of man. 



Throughout the two volumes of Animals and Plants under 

 Domestication, one sees it was Darwtn's task to prove, by over- 

 whelming cumulative evidence, that an accumulation of variations 

 under natural or artificial selection could lead to the formation of 

 new species. His work was not to examine hoiv variations arise ; 

 but this still deeply mysterious question is the one of chief impor- 

 tance to the present generation, to whom the fact of the evolution 

 of species, which Darwin laboured to establish, is a truism. 



I have had room to give only a very few of the wealth of 

 interesting facts in this wonderful work of Darwin ; and I must 

 leave the evidence as to Graft-Hybrids, perhaps at this day the 

 most interesting and important of all, for another paper. 



* Ibid., pp. 305—6, Vol. II., p. 212, 329—31. 



