BASIS OF THE PKOBLEM G7 



degree or in kind from the former characters under other stimuh. 

 It is altogether misleading to speak of anything but predisposi- 

 tions as present in the germinal constitution, though, of course, for 

 the sake of brevity other phraseology may be employed once this 

 point is understood. When, therefore, we speak of the inheritance 

 of any character, we mean that there is a predisposition in the 

 germinal constitutions both of the parent and of the offspring to 

 develop this character under certain stimuli, which stimuli must 

 play both upon the parent and upon the offspring if the character 

 is to be manifested in both of them. 



If we have to regard the germinal constitution as somehow 

 containing very many separate predispositions or, as they are 

 often called, factors, is it in the second place possible to say in 

 what these factors consist ? No definite answer to this question 

 can as yet be given. Certain hypotheses have been put forward. 

 Weismann, for instance, suggested that the factors were to bo 

 sought in groups of molecules of chromatin. It is not necessary, 

 however, to postulate definite and separate particles as the 

 physical basis of the predispositions. The protoplasmic molecule 

 is a very complex structure consisting of a very large number of 

 atoms. Similar atoms may be differently grouped within a mole- 

 cule, and different predispositions may well be functions of 

 different groupings. 



3. In order that we may answer the first of the two problems 

 set out at the beginning of the chapter we must consider in rather 

 more detail in what the development of an organism consists.^ 

 Every character is, as we have seen, the result of the influence 

 of the environment upon what is innately given. If two indivi- 

 duals were endowed with precisely similar germinal constitutions, 

 and if precisely similar stimuli played upon each of them, then 

 the adult forms would be similar in respect of all their characters. 

 But if the stimuli are not similar, if, for instance, more food is 

 provided in one case than in another, then, though the germinal 

 constitutions are similar, one adult may be larger than the other. 

 Again, let us suppose that the germinal constitutions differ, that, 

 for instance, there is in one case a predisposition to the develop- 

 ment of greater size than in the other, then, even if the stimuli 



' In this and the following sections I am indebted to Professor Goodrich's 

 admirable treatment of these problems in his book, The Evolution of Living 

 Organisms. 



E 2 



