THE ORIGIN OF LIFE. 51 



and how strongly the law of continuity is establish- 

 ing itself in the light of discovered fact, we must 

 admit that there is a significance in speculations on 

 the origin of life which is deeper than at first sight 

 appears. 



Protoplasm Not the Simplest Basis of Life. 



In the discussion which has gone before, proto- 

 plasm has been referred to as if it were a definite 

 chemical compound, though one of great complex- 

 ity. It has seemed to many that the first step in 

 the history of life must have been the production of 

 a protoplasmic mass like some of our present low 

 organisms {Myxomycetes}. But nothing is more 

 certain than that protoplasm is not a definite sub- 

 stance, and that it is by no means uniform in differ- 

 ent organisms. It is found to differ widely in its 

 physical nature, sometimes being almost solid, some- 

 times very liquid. It is found to differ more or less 

 in its chemical composition, no two analyses agreeing 

 exactly, and when we take its functions into consid- 

 eration, the differences between different specimens 

 of protoplasms become extreme. Although the 

 amoeba and the nerve cell of the human brain are 

 both composed of protoplasm, how wide are the 

 differences between the powers they possess. Plant 

 protoplasm is capable of making use of the energy 

 of sunlight, while animal protoplasm is not. When 

 we call protoplasm " the physical basis of life," and 

 try to prove the unity of the organic world by its 

 universal presence in all living things, we have not 

 by any means reached the bottom of the matter. 



