THE STUDY OF HEREDITY 339 



course of events. Besides, it does not seem to me worth while 

 to preserve and breed from thousands of undesirables in order 

 to avoid the possible loss of one desirable individual. Prof. 

 Davenport's book shows that the production of the efficient by 

 inefficient parents is very rare, whilst efficient parents commonly 

 produce efficient children. 



The question as to what proportion of undesirable traits may 

 be modificational is a very important one, and one upon which it 

 is very easy to fall into serious errors. It involves the question 

 of the inheritance of acquired characters to some extent. The 

 question to deal with is — which of the characters of the adult 

 organism are acquired and which inborn ? We speak of them 

 as those due to " nurture " and " nature" respectively; as being 

 in fact divided into two distinct and easily separated groups. 

 As Dr. Archdall Reid has pointed out, they are not to be thus 

 easily distinguished. Every multicellular organism begins its 

 existence as a single cell, the fertilised ovum ; it is quite 

 evident that the characters of the adult organism cannot be 

 present as such in a single cell. What then represent the 

 characters of the adult organism in the ovum ? The capacity to 

 develop along certain lines within certain comparatively narrow 

 limits under certain conditions. We may regard the ovum as a 

 portion of very complex matter of such a nature and so shaped 

 that additions can only be made to it in certain very definite 

 directions and in certain very definite ways, with the result 

 that it is capable of growing only into a particular form with 

 particular characters. It is then these capacities for develop- 

 ment along particular lines, these potentialities, which are 

 inborn. The resulting development of these capacities must 

 obviously be modified from the very first by the environment. 

 The amount of possible modification by the environment varies 

 enormously in different organisms. In the butterfly it is extra- 

 ordinarily small ; in man it is extraordinarily great. This great 

 dependence of man upon modifications by the environment has 

 led many people to attach too great importance to it and not 

 enough to the inborn capacities. Take any class of school-boys. 

 No two boys will show the same capacity for obtaining know- 

 ledge and skill in any given subject ; the boy who is above the 

 average capacity in one may be below it in another, though most 

 will be able to reach an average standard in all. Now it is quite 

 evident that in such cases the difference in the environment is 



