128 MENDELISM CHAP. 



latter have been termed fluctuations, and at present 

 we have no valid reason for supposing that they are 

 ever inherited. For though instances may be found 

 in which effects produced during the lifetime of the 

 individual would appear to affect the offspring, this 

 is not necessarily due to heredity. Thus plants 

 which are poorly nourished and grown under adverse 

 conditions may set seed from which come plants 

 that are smaller than the normal although grown 

 under most favourable conditions. It is natural 

 to attribute the smaller size of the offspring to the 

 conditions under which the parents were grown, and 

 there is no doubt that we should be quite right in 

 doing so. Nevertheless, it need have nothing to do 

 with heredity. As we have already pointed out, the 

 seed is a larval plant which draws its nourishment 

 from the mother. The size of the offspring is 

 affected because the poorly nourished parent offered 

 a bad environment to the young plant, and not 

 because the gametes of the parent were changed 

 through the adverse conditions under which it grew. 

 The parent in this case is not only the producer of 

 gametes, but also a part of the environment of the 

 young plant, and it is in this latter capacity that it 

 affects its offspring. Wherever, as in plants and 

 mammals, the organism is parasitic upon the mother 

 during its earlier stages the state of nutrition of the 

 latter will almost certainly react upon it, and in this 

 way a semblance of transmitted weakness or vigour 

 is brought about. Such a connection between mother 

 and offspring is purely one of environment, and it 

 cannot be too strongly emphasised that it has nothing 

 to do with the ordinary process of heredity. 



