THE CROSSING, AC, OP PIGEONS AND FOWLS. 219 



nated and disappeared," and to have appeared again, 

 "within this same period," of two hundred and odd 

 years. He also refers to, and records the many breeds 

 which "have become extinct" (p. 508, Vol. ii, Animals 

 and Plants, &c). 



The reason, that these fancy varieties continue their 

 breed the length of time that they do, is, because, first, 

 the differences, between the individuals of each variety, 

 serve, in a measure, to stave off the evil effects for a 

 time ; secondly, because these varieties frequently cross ; 

 and, thirdly, because these varieties change their forms, 

 from time to time, by means of the action of reversion 

 in some of their characters, and of the influence of 

 Man's Selection. 



Darwin says (p. 262, Vol. ii, Animals and Plants, &c.) : 



" Fashions do, to a certain extent, change ; first, one 

 point of structure, and then another, is attended to." 

 And again he says, " The fancy ebbs and flows." 



This fashion and fancy are quite frequently controlled 

 and directed, unconsciously to man, by the fact that 

 health and breeding capacity are to be found, only in 

 those individuals which depart in some point from the 

 defective, varietal type. Man, therefore, in picking out 

 the strong individuals and the good breeders, unwit- 

 tingly changes the form of the variety. 



With improved breeds of horses, of sheep, and of 

 cattle, there is a probability of their being able to con- 

 tinue their line, for many centuries, because they gener- 

 ally approximate the full and proportionate develop- 

 ment of their respective species. 



