EVOLUTION IN GENERAL 281 



such a process and that it may only be modified by prayer to a 

 Divine agency may be repugnant to them — as scientific men, of 

 course. 



iv. A Resume. We believe then : 



id) that there is some agency in the ovum, spermatozoon, spore, 

 bud, or other undeveloped organism, that evolves in the course 

 of the developmental process. This is the " organization " and 

 we do not know what it is. In the course of the development the 

 undifferentiated organism evolves so that, by interaction with 

 the energies and materials of the environment, it assumes the 

 functional-structural configuration that is described by the char- 

 acters of a species. The organization w^e regard as an ensemble 

 of potentialities and this ensemble is a different one in the ova, 

 spermatozoa, spores, buds, etc., of every organic species. 



{h) Changes may occur in the organization so that the potentiali- 

 ties change. Every such change is called a " mutation." We 

 associate the potential change with the parts of the undeveloped 

 organism called the " germ-plasm," " chromosomes," etc., but 

 we do not know what, physically speaking, is the change. Having 

 once changed the same change is *' inherited," that is, it reappears 

 in the next generation of ova, spermatozoa, etc. If the change 

 tends towards longer life and greater power of reproduction 

 '* selection " is said to have occurred and evolution, in the Dar- 

 winian mode, takes place. 



(c) The developed organism has still, to some extent, the 

 potentialities of change and it may, as the expression of some 

 *' needs or desires," change its methods of behaviour and function- 

 ing, and also its structure. It is believed that such changes, 

 acquired by the developed organism, may affect the potentialities 

 of its ova, etc., so that the acquired change may become an 

 inheritable one. If the change leads to longer life and greater 

 power of reproduction selection is said to have occurred and there 

 is evolution. 



{d) These hypotheses of evolution are still largely logical ones 

 and are the subjects of controversy. 



We have now to discuss the evolutionary process as something 

 that has actually occurred. The evidence that an evolutionary 

 career has occurred is the existence of records of life, in the past, 

 in the forms of fossils. We have, first, to interpret the natures 



