ECTOPLASM AND EVOLUTION 



for instance in the fertilization of the egg. In tissues highly 

 endowed with conductivity, as in those highly endowed 

 with contractility, the predominating characteristic is rela- 

 tively large surface area. In nerve cells, conduction travels 

 over the nerve fibre (ectoplasmic prolongation), and is 

 transferred by means of ectoplasm from one unit to another. 

 By and large, it is reasonable to assume that both contrac- 

 tility and conductivity are greater in surface-rich than in 

 surface-poor protoplasm. 



The subsequent differentiation from a hypothetical first 

 form of life into animal or plant we may suppose came about 

 through the higher development of contraction and of con- 

 duction by that form which evolved as animal. A deviation 

 or less emphasis on these brought plants as such into being. 

 It is surely on the side of the nervous tissue that animals 

 and plants differ most. 



Cellular oxidation is a function of cytoplasmic structure. 

 Again it is reasonable to assume that oxygen coming into 

 the cell makes first some union with the superficial cyto- 

 plasm, as we have seen. 



Now of three fundamental life-processes — contraction, 

 conduction and respiration — respiration may be regarded 

 as primary: on it depends all vital activity. Respiration, 

 the same in both animals and plants, may have been largely 

 responsible for the early separation between plant and 

 animal. That is, those primordial individuals possessing 

 most rapid rates of oxygen-consumption tended to oxidize 

 themselves, or as cannibals, their like. Some, because of 

 lesser intake of oxygen, tended to accumulate CO2 and thus 

 developed photosynthetic power as a means of protection. 

 With this went also the building up from COo and water of 

 carbohydrate polymers, including cellulose.^ The presence 

 of cellulose determined the disposition of the cytoplasm 

 found in higher plants — that is, a cytoplasm of peripheral 



Cf. also Geddes. 



359 



