DURATION 01 RACES. 339 



ety has turned up since, but because a presumption 

 has been raised under which the evidence would take 

 a bias the other way. There is now in the minds of 

 scientific men some reason to expect that certain vari- 

 eties would die out in the long run, and this might 

 have an important influence upon the interpretation 

 of the facts. Curiously enough, however, the recent 

 discussions to which onr attention has been called 

 seem, on both sides, to have overlooked this 



But, first of all, the question needs to be more 

 specifically stated. There are varieties and varieties. 

 They may, some of them, disappear or deteriorate, but 

 yet not wear out not come to an end from any inher- 

 ent cause. One might even say, the younger they are 

 the less the chance of survival unless well cared for. 

 They may be smothered out by the adverse force of 

 superior numbers; they are even more likely to be 

 bred out of existence by unprevented cross-fertiliza- 

 tion, or to disappear from mere change of fashion. 

 The question, however, is not so much about reversion to 

 an ancestral state, or the falling off of a high-bred stock 

 into an inferior condition. Of such cases it is enough 

 to say that, when a variety or strain, of animal or vege- 

 Ijable, is led up to unusual fecundity or of size or prod- 

 wet of any organ, for our good, and not for the good 

 * F$jie plant or animal itself, it can be kept so only by 

 high feeding and exceptional care ; and that with high 

 feeding and artificial appliances comes vastly increased 

 liability to disease, which may practically annihilate 

 the race. But then the race, like the bursted boiler, 

 could not be said to wear out, while if left to ordinary 

 conditions, and allowed to degenerate back into a more 



