140 THE PHILOSOPHY OF BIOLOGY 



Or perhaps it means, and this is the better way of 

 putting it, that the " organisation," whatever it may 

 be, depends on size. We see this very clearly in the 

 experiment of cutting in two the blastula of the sea- 

 urchin. If the pieces are of approximately equal size 

 each will form an entire Pluteus larva, but if one of 

 them is below a certain limit of size it will not continue 

 to develop. The " organisation," therefore, has a 

 certain volume, and this volume is much greater than 

 that of any one of the cells of which the fragment 

 exhibiting it is composed. It is enormously greater 

 than the volume of any group of determinants which 

 we can imagine to represent the different kinds of cells 

 composing the body of the Pluteus larva, and still 

 more enormously greater than the volume of a " mole- 

 cule ' of protoplasm. Now this association of 

 " organisation " and size is of immense philosophical 

 importance, for it does away, once and for all, with the 

 idea that the ' organisation ' is solely a series of 

 chemical reactions. If it were, one cell of the blastula 

 would contain it, for on the mechanistic hypothesis 

 one cell, the egg-cell, contains it, and this cell can be 

 divided innumerable times and still contain it. The 

 egg is a complex equip otential system (Drieseh), which 

 divides again and again throughout innumerable 

 generations, and still contains the " organisation." 



It is in vain that we attempt the misleading analogy 

 of the " mass action " of physical chemistry, to show 

 that volume may influence chemical action. In such 

 a mass action what we have is this : — 



A a + B b ±^ C c + D d 



the letters A , B and C standing for chemical substances 

 present, and the letters a and b, etc., representing the 



