ORIGIN OF LIFE, SEX, SPECIES, ETC. 219 



their original energy at every step. When they 

 reach the center, they must therefore be in a very 

 much enfeebled condition. This is a further reason 

 why the outer substance of a cell is in a very 

 high degree subject to changes from external influ- 

 ences, while the central substance, on the contrary, 

 if at all, is but slightly so. 



From this it follows that with the birth of a cell 

 a process begins which tends to differentiation in its 

 external parts, and which leaves the central sub- 

 stance almost unaffected. The longer the life of a 

 cell, the greater the opportunity for concentration 

 of like with like within it. The greater the mass of 

 the cell, the greater the freedom of the central sub- 

 stance from disturbance by environmental move- 

 ments and influences. The more purely alike the 

 particles of an organic mass, the more correctly 

 does it represent the nature and character and 

 potentialities of its own kind of protoplasmic com- 

 pounds. Thus it follows that in unicellular or- 

 ganisms the instant when they come into existence 

 the central substance begins to be ever more special- 

 ized to perpetuate the original characteristics arising 

 from the nature and composition of the compounds 

 from which their particular form of life originally 

 descended. It becomes the carrier of the hereditary 

 traits of the special class of life to which it belongs. 

 The external substance, on the contrary, by the same 

 process acquires an extreme liability to variation by 

 external influences. The circulatory motions of the 



