APPENDIX B 371 



Mendelian sense) but we shall seldom discover characters which 

 have previously been latent. Thus, if varieties of men be crossed, 

 not a single latent character is revealed. 1 It would be too much 

 to say that no latent characters occur in natural varieties, but 

 unquestionably they seem far from common, I am not aware 

 that any instances of latency have been recorded among 

 parthenogenetic or self-fertilized species. 



The evolution that results from artificial selection differs 

 from that which results from Natural Selection mainly in 

 that it is much more rapid. The breeder, paying scant attention 

 to other characters, chooses the largest favourable variation in 

 the particular character he wishes to develop. It seems probable, 

 then, that characters tend most to become permanently latent 

 when selection is most stringent and evolution most rapid. The 

 Mendelian doctrine does not explain this permanent kind of 

 latency. According to it the allelomorphs meet in the zygote 

 (the fertilized ovum) only to separate in the descendant gametes 

 (the sperms and ova). This separation, however, has only been 

 surmised. It cannot, of course, be seen. Even if it occurs 

 it is certainly incomplete, for, as we have seen, in many instances 

 some degree of blending is observable. It is a question 

 whether it ever really occurs, for on the hypothesis that allel- 

 omorphs are interchangeable but not combinable, the blending 

 is difficult to explain. A link between permanent and Mendelian 

 latency is furnished when species alternate parthenogenetic with 

 bi-parental reproduction. Here the male allelomorphs do not 

 separate from their opposite numbers ; they merely become latent 

 for a more or less prolonged period ; they may, indeed, be rendered 

 permanently latent by various circumstances in aphides by 

 supplying the animals with plenty of food and preserving a 

 continuously warm temperature. Similarly it is conceivable that 

 in pure " derived " dominants and recessives the opposite numbers 

 are not really absent but only permanently latent. If this be so, 

 since the breeder chooses as large variations as possible, since 

 large favourable variations occurring simultaneously in two in- 

 dividuals, male and female, are not very common, he is often 



1 Darwin (Animals and Plants, vol. ii., p. 21) mentions a number of half- 

 caste races as having very bad dispositions, and adds, "From these facts we 

 may perhaps infer that the degraded state of so many half-castes is in part 

 due to reversion to a primitive and savage condition, induced by the act of 

 crossing, even if mainly due to the unfavourable moral conditions under which 

 they have been reared." But there appears no valid reason for attributing 

 any part of the moral delinquency of half-castes to reversion. Racial mental 

 peculiarities of this sort are acquired, not innate. (See 468.) Darwin himself 

 says, "That many excellent and kind-hearted mulattos have existed no one 

 will dispute. And a more mild and gentle set of men could hardly be found 

 than the inhabitants of the island of Chiloe, who consist of Indians commingled 

 with, Spaniards in various proportions. " 



