6 THEORY OF ORGANIC EVOLUTION. 



In the primordial condition this balancing process 

 is irregular and accidental and remains so even later 

 in many of the lowest organisms. Little by little 

 it becomes phylogenetically more regular by indi- 

 viduals attaining to a more definite size and term of 

 life, while only the germs detached from them 

 remain viable. This phenomenon known as repro- 

 duction has a double origin. 



A. The portions of primordial plasma that grow 

 to a more considerable size as soft, half-liquid 

 masses break up by the mechanical action of exter- 

 nal circumstances into smaller portions of indefinite 

 number and size. This typifies irregular and acci- 

 dental reproduction of the lowest order. 



In the offspring of the primordial plasma division 

 becomes gradually more and more regular as a 

 result of the increasing organization of the sub- 

 stance, and especially as a result of the formation of 

 an envelope about it, till finally in the microscop- 

 ically small masses, which are now called cells, 

 division into two parts always appears, after these 

 masses have grown to perhaps double their original 

 size. After division the two halves separate from 

 each other and represent independent individuals. 



In the further course of phylogeny the division 

 of the cells into two parts takes place regularly. 

 But the cells remain united to each other and form 

 multicellular individuals, which increase by cell 

 division and which at times in the lowest stages are 



