THE ORGANIC AND THE INORGANIC 307 



ance of planktonic life are really misleading, for although 

 a single drop of water may contain some hundreds of 

 organisms, the mass of these is exceedingly small and 

 is usually expressed as one or two parts per million. 

 All this means that life has difficulty in manifesting 

 itself in material forms. Whether it be simply a mode 

 of interaction of some complex chemical substances 

 with a relatively simple physico-chemical environment 

 -the mechanistic view or whether it be an impetus 

 or agency which is neither physical nor chemical, but 

 which acts through physical and chemical elements 

 the vitalistic view, life is capable of acting on terrestrial 

 materials to a very limited extent. Acting through all 

 the tendencies which \ve see to exist in it, life may be, 

 so to speak, diluted ; but by being concentrated in one 

 or a few of them it becomes more effective. The dis- 

 sociation of this bundle of tendencies which we call life 

 is therefore the meaning of the evolutionary process. 



Ontogenetic development, says Roux, is the pro- 

 duction of a visible manifoldness. It cannot be said 

 that this cautious description of the developmental 

 process has been apprehended by those who expound 

 the dogmas of mechanistic biology. Development is 

 indeed the production of a diversity, but this diversity 

 is only a phase of a preceding diversity, a rearrangement 

 of spatially extended pre-existing elements. How else 

 could the developing embryo and its material environ- 

 ment be regarded as a system of physico-chemical 

 elements, capable of study by the methods of experi- 

 mental and mathematical physics, except by regarding 

 it as a system passing through phases each of which is 

 a necessary consequence of the preceding one, and each 

 of which contained the same elements separated from 

 each other in space ? Let us think of water occupying 

 a vessel at a high temperature and continually cooling. 



