LIVING SUBSTANCE 



57 



tention of observers soon after the discovery of the microscope. It 

 was found that this remarkable creature could be divided by a 

 cross-cut into two halves, each one of which could transform itself 

 again into a complete, but correspondingly smaller individual. 

 The anterior half, bearing the tentacles, simply closes up the wound 

 and attaches itself again at its posterior end, while from the 

 posterior half new tentacles soon sprout out from the edges of the 

 wound, and in a short time both pieces have become complete 

 Hydras. The halves can be divided still further, and the animal 

 can even be cut into a large number of small pieces, each one of 

 which can transform itself into a complete individual. The 

 unitary individual has thus been divided into two or even several 

 individuals. If, therefore, indivisibility alone be the standard of 



FIG. 2. Hydra fusca, a fresh-water polyp ; A, cut across at * ; .Band C, the two pieces, which have 

 become regenerated into two complete individuals. 



individuality, Hydra is not an individual, for it can be divided 

 without the loss, by the pieces, of the characteristics of the original 

 animal ; and the same is true of every tree and every shrub. 



The criterion of the individual is, therefore, not to be found in 

 indivisibility, but rather in undividedness or unity. So long as 

 Hydra was undivided, it was an individual, a whole, a unit. By 

 the division, however, the original individual came to an end and 

 from it two new units arose which, so long as they are not further 

 cut into pieces, represent complete individuals. Hence the fact of 

 unity alone is decisive in defining the conception of individuality, 

 if the latter is to be stated in such general terms that it holds good 

 for all special cases. An organic individual would accordingly be 

 merely a unitary mass of living substance. 



But iri*this very general form the definition is too broad. Ac- 

 cording to it a small particle of living substance, cut off from the 



