Chap. XV. oF UNIFORMITY OF CHAKACTER. 67 



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the act of c]'0>sin<2: in itself tends to brins; back lono;-los1 

 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 indigenous breeds, it will rarely or never occur 

 that both are equally well adapted to the surrounding cir- 

 cumstances ; more especially when permitted., to roam freely, 

 and not carefully tended, as is generally the case with breeds 

 allowed to cross. As a consequence 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 w^ould require before such a crossed body 

 of animals would assume a uniform character within a limited 

 area, 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 characters thus acquired 

 would rarely or never, as may be inferred from the previous 

 considerations, be exactly intermediate between those of the 

 two 23arent-breeds. With respect to the very slight differences 

 by which the individuals of the same sub-variety, or even of 

 allied varieties, are characterised, it is obvious that free 

 crossing would soon obliterate such small distinctions. The 

 formation of new varieties, independently of selection, would 

 also thus be prevented ; except when the same variation 

 continually recurred from the action of some strongly pre- 

 disposing cause. We may therefore conclude that free 

 crossing has in all cases played an important part in giving 

 uniformity of character to all the members of the same 

 domestic race and of the same natural species, though largely 

 governed by natural selection and b^^ the direct action of the 

 surrounding conditions. 



On the ijossihility of all organic hcings occasionally infer'crossing. 

 — But it may be asked, can free crossing occur with herma- 

 phrodite animals and plants ? All the higher animals, and 

 the few insects which have lieen domesticated, have separate 



