56 ANIMAL INDIVIDUALITY [CH. 



process. The actual division seems to be effected by 

 a mere temporary lessening of surface-tension in 

 certain regions, so that this would probably be the 

 way of least resistance for the organism, the way that 

 involved less deep-seated change than the first method. 

 In its results it is certainly better. The species (by 

 which is meant simply the kind of protoplasm), by the 

 repeated formation and subsequent wandering away 

 of new separate masses of protoplasm, is widely dis- 

 persed, so that it no longer presents a single neck by 

 the severing of which some Nero of an accident could 

 with one stroke exterminate the race. 



It is thus almost entirely a direct result of the 

 essential properties of protoplasm, scarcely at all an 

 adaptation to outer conditions, that the earliest forms 

 of life defined and limited their size ; in other words, 

 that the first stable phase reached by life in her 

 development on this earth was one in which she 

 manifested herself as a succession of separate pro- 

 toplasmic units, each formed from the bipartition of 

 a former one, each beginning its existence as a rounded 

 body of definite but always microscopic size, and each 

 gradually growing, while preserving its form, till its 

 volume was about doubled, when it divided and left 

 its two halves to repeat the cycle. These, the primary 

 units of life, are usually called by the name of cells 1 , 



1 Some biologists wish to restrict the term cell to protoplasmic 

 units with a formed nucleus. The nucleus, however, has certainly 



