1900.] on Facts of Inheritance. 353 



in the inheritance. Indeed, the fact that the resemblance so often 

 re-appears in the third generation, makes it probable that the in- 

 completeness is not in the inheritance, but simply in its expression. 

 The characters which seem to be absent, to " skip a generation," 

 as we say, are probably part of the inheritance, as usual. But they 

 remain latent, neutralised, silenced (we can only use metaphors) by 

 other characters, or else unexpressed, because of the absence of the 

 appropriate stimulus. 



We can imagine the son of a lavish millionaire reacting to plain 

 living; we can imagine the superficial supposition that the money 

 had been lost ; and we can imagine the complete contradiction of 

 this inference in the third generation. 



(a) In blended inheritance, the characters of the two parents, e.g. 

 in regard to a particular structure, such as the colour of the hair, may 

 be intimately combined in the offspring. This is particularly well 

 seen in some hybrids, where the offspring seems like the mean of the 

 two parents ; it is probably the most frequent mode of inheritance. 



(b) In exclusive inheritance, the expression of maternal or of 

 paternal characters in relation to a given structure, such as eye-colour, 

 is suppressed. Sometimes the unilateral resemblance is very pro- 

 nounced, and we say that the boy is " the very image of his father," or 

 the daughter " her mother over again " ; though even more frequently 

 the resemblance seems " crossed," the son taking after the mother, 

 and the daughter after the father. Our emphasis on the distinction 

 between inheritance and the expression of inheritance is surely 

 warranted by cases on record where the young boy resembled the 

 mother and the girl the father ; but when they came of age, the 

 likeness was reversed, i.e. formerly obscure resemblances became 

 dominant. 



(c) It seems convenient to have a third category for cases where 

 there is neither blending nor exclusiveness, but where in the ex- 

 pression of a given character, part is wholly paternal and part wholly 

 maternal. This is called particulate inheritance. Thus, an English 

 sheep-dog may have a paternal eye on one side, and a maternal eye 

 on the other. Suppose the parents of a foal to be markedly light 

 and dark in colour ; if the foal is light brown the inheritance in that 

 respect is blended, if light or dark it is exclusive, if piebald it is 

 particulate. In the last case there is in the same character an ex- 

 clusive inheritance from both parents. 



The numerous experiments on hybridisation made by botanists, 

 zoologists, and more practical people, have led us to expect one of 

 three results when a crossing has a successful issue. (1) The hybrid 

 may be intermediate between its parents, sometimes so exactly that 

 we may liken the blending, not merely to warp and woof, but to a 

 mingling of two colours; (2) the hybrid may show an exaggeration 

 of the characters of one parent, often with little apparent realisation 

 of the peculiarities of the other. These correspond to blended and 

 exclusive inheritance in ordinary cases of mating within the same 



