DENIALS OF INHERITANCE 25 



the water, are conditions of embryonic coherence ; others, like light 

 and heat, serve to accelerate or to inhibit. It seems, also, that par- 

 ticular combinations of factors are required as the " liberating 

 stimuli" of particular characters in the developing organism. De- 

 velopment is the expression of the inheritance, and the fullness of the 

 expression depends on there being a normal environment. What is 

 called a hereditary defect may be simply a defect in expression due 

 to inadequate environment. 



How fundamental the germinal nature is may be realised if we think 

 of Heape's experiment of transferring the fertilised ovum of a long- 

 haired white angora rabbit into another variety of rabbit — a short- 

 coated gray Belgian hare. The young were not less long-haired or 

 less white because of the transplantation of the ova. Similarly 

 Castle and Phillips removed the ovaries from a white albino guinea- 

 pig, inserted those of a young black individual, and had the grafted 

 animal mated with a male albino. Normal albinos mated together 

 always have albino young, but the animal experimented on had to the 

 albino male three litters (six young) all black. The foster-body did 

 not count. 



2. Beneath the misunderstanding which has led some to deny 

 the facts of inheritance there is, as we have seen, a reasonable 

 though exaggerated recognition of the potency of similar function 

 and environment in producing resemblance ; and there is, per- 

 haps, the recognition of another fact — that of variation. For 

 several reasons — for instance, because the new life usually springs 

 from a fertilised ovum which combines maternal and paternal 

 contributions — the child is never quite like its parents. In other 

 words, we suppose that the germinal material from which a 

 child develops is not quite the same as that from which the parents 

 developed, or not quite the same as that from which its brothers 

 and sisters developed, and the result is variation in the true 

 sense. Each offspring has its individuality and is a new creation. 

 Even within a family no two are alike, especially to the care- 

 ful parent's eye, though the impartial onlooker may be struck 

 by the monotony. On the one hand, " Alle Gestalten sind 

 ahnlich " ; on the other, " Keine gleichet der andem." 



