NATURE AND NURTURE 7 



and reaction must be regarded as rigorously determined by the 

 parental and ancestral contributions, the nurture — the en- 

 vironmental influences — must not be thought of as pre-deter- 

 mined. In fact, the surrounding influences are very variable, 

 and the nature of the young organism may be profoundly 

 changed by them. Thus, we soon find it possible to distinguish 

 between the main features, which are the normal realisations 

 of the inheritance in a normal environment, and peculiarities 

 which are due to peculiarities in nurture. The characters of a 

 newly-hatched chick stepping out of the imprisoning egg-shell 

 are in the main strictly hereditary ; but they need not be alto- 

 gether so, for during the three weeks before hatching there has 

 been some opportunity for peculiarities in the environment to 

 leave their mark on the developing creature. Still more is 

 this the case with the typical mammalian embryo, which develops 

 often for many months as a sort of internal parasite within the 

 mother — in a complex and variable environment. And as life 

 goes on, peculiarities due to nurture continue to be superimposed 

 on the hereditary qualities. 



William of Occam's Razor. — Our preliminary attempt to get 

 rid of capitals, to make the terms heredity and inheritance quite 

 objective, is in line with what has occurred in other departments 

 of science. For one of the distinctive features of the nineteenth 

 century has been a reduction in the number of supposed separate 

 powers or entities— the use of William of Occam's razor, in fact. 

 " Entia non sunt mnltiplicanda prceter necessitatem." " Caloric " 

 was one of the first to be eliminated, yielding to the modern 

 interpretation of heat " as a mode of motion " ; " Light " had 

 to follow, when the undulatory or the electro-magnetic theory 

 of its nature was accepted ; a specific " Vital Force " is disowned 

 even by the Neo-vitalists ; " Force " itself has become a mere 

 measure of motion ; and even " Matter " tends to be resolved 

 into units of negative electricity, carrying with them a bound 

 portion of the ether in which they are bathed; and so on. In 



