38 THE EVOLUTION THEORY 



are very considerable, for, according to Darwin, one of the largest 

 runt-pigeons weighed exactly five times as much as one of the 

 smallest tumblers with short forehead, and in the illustration (Fig. i) 

 the pouter looks a giant beside the little barb to its left. 



Thus we see that nearly every part of the body of the pigeon has 

 varied under domestication in the most diverse ways, and to a high 

 degree : and the same is true of several other domesticated animals, 

 poultry, horses, sheep, cattle, pigs, and so on, though the matter is not 

 altogether so clear in their case, since descent from a single wild 

 species cannot be proved, and is in many cases improbable. But in 

 the case of pigeons this common descent is certain, and we have now 

 to inquire in what manner all these variations from the parent form 

 have been brought about. 



The answering of this question is rendered easier by the fact 

 that new breeds arise even now, and that, to some extent at least, 

 they can be caused to arise, consciously and intentionally. In 

 England, as well as in Germany and France, there are associations for 

 the breeding of birds, and in England especially pigeon and poultry 

 clubs are numerous and highly developed. These by no means confine 

 themselves to simply preserving the purity of existing breeds, they 

 are continually striving to improve them, by increasing and accentu- 

 ating their characters, or even by introducing quite new qualities, 

 and in many cases they succeed even in this last. Prizes are offered 

 for particular new variations, and thus a spirit of rivalry is fostered 

 among the breeders, and each strives to produce the desired character 

 as quickly as possible. Darwin says : ' The English judges decided 

 that the comb of the Spanish cock, which had previously hung 

 limply down, should stand erect, and in five years this end was 

 achieved ; they ordained that hens should have beards, and six years 

 later fifty-seven of the groups of hens exhibited at the Crystal Palace 

 in London were bearded.' The transformation does not always come 

 about so quickly, however: thus, for instance, it required thirteen 

 years before a certain breed of tumblers was furnished with a white 

 head. But the breeders cause every visible part of the body to vary 

 as seems good to them, and within the last fifty years they have 

 really brought about very considerable changes in many breeds. 

 Their method of procedure is carefully to select for breeding those 

 birds which already possess a faint beginning of the desired character. 

 Domesticated animals have on the whole a higher degree of variability 

 than wild species, and the breeder takes advantage of this. Suppose 

 it is a question of adding a crown of feathers to a smooth-headed 

 breed, a bird is chosen which has the feathers on the back of the 



