Chap. XV. OF UNIFORMITY OF CHARACTER. 89 



depend largely on the conditions of life being favourable to any 

 particular character ; and we may suspect that there would be 

 under the climate of Germany a constant tendency to degene- 

 ration in the wool of Merinos, unless prevented by careful 

 selection ; and thus perhaps the foregoing remarkable case may 

 be explained. The rate of absorption must also depend on the 

 amount of distinguishable difference between the two forms 

 which are crossed, and especially, as Gartner insists, on pre- 

 potency of transmission in the one form over the other. We 

 have seen in the last chapter that one of two French breeds 

 of sheep yielded up its character, when crossed with Merinos, 

 very much slower than the other; and the common German 

 sheep referred to by Fleischmann may present an analogous 

 case. But in all cases there will be during many subsequent 

 generations more or less liability to reversion, and it is this fact 

 which has probably led authors to maintain that a score or more 

 of generations are requisite for one race to absorb another. In 

 considering the final result of the commingling of two or more 

 breeds, we must not forget that the act of crossing in itself 

 tends to bring back long-lost characters not proper to the 

 immediate parent-forms. 



With respect to the influence of the conditions of life on any 

 two breeds which are allowed to cross freely, unless both are 

 indigenous and have long been accustomed to the country where 

 they live, they will, in all probability, be unequally affected by 

 the conditions, and this will modify the result. Even with indi- 

 genous breeds, it will rarely or never occur that both are equally 

 well adapted to the surrounding circumstances ; more especially 

 when permitted to roam freely, and not carefully tended, as will 

 generally be the case with breeds allowed to cross. As a con- 

 sequence of this, natural selection will to a certain extent come 

 into action, and the best fitted will survive, and this will aid in 

 determining the ultimate character of the commingled body. 



How long a time it will require before such a crossed body 

 of animals would assume within a limited area a uniform cha- 

 racter no one can say; that they would ultimately become 

 uniform from free intercrossing, and from the survival of the 

 fittest, we may feel assured; but the character thus acquired 

 would rarely or never, as we may infer from the several previous 



