300 THE PHILOSOPHY OF BIOLOGY 



molecules, and which therefore lay outside each other 

 in the same sense. 



The evolution of the individual organism must be 

 a process of the same kind. Like cosmic and phylo- 

 genetic evolution, it is apparently a progress from the 

 simple to the complex. A minute fragment of proto- 

 plasmic matter, homogeneous in composition, or ap- 

 parently so, grows and differentiates, becoming the 

 complex structure of the adult organism. Here the 

 system in the physical sense is the fertilised ovum, the 

 oxygen and nutritive matter which have become in- 

 corporated with it, and the physical environment with 

 which these things interact. All these elements existed 

 in that phase of the system which contained among its 

 parts the fertilised ovum, as well as in that phase which 

 contained the fully developed organism. Complex by 

 comparison with the fertilised ovum and its environ- 

 ment as the adult animal and its environment may 

 seem to be, it is only a different phase of the same 

 system. Further, all the parts that form the tissues 

 of the adult, and all their motions, are spatially ex- 

 tended, and are only rearrangements of the molecules 

 and of the motions of the molecules that were actually 

 present in the system in its initial phase. Speculation 

 along these lines has led to all the results of Weismann- 

 ism. All the parts of the adult organism are really 

 present in the fertilised ovum and the nutritive matter 

 which is to build up the fully developed animal, not in 

 potentiality it must be noted, but actually present in 

 the spatially extended condition. It is true that the 

 hypothesis only requires that the determinants of the 

 adult organs and tissues, and of the adult qualities, 

 should be present in the ovum ; but since the energies 

 necessary for the separation of these determinants, and 

 for their arrangement and growth in mass, must also be 



