10 EVOLUTION BY ATROPHY 



We shall justify the distinction we make by 

 showing that colonies are entirely distinct from 

 societies. The two are divergent branches which 

 spring from the same source, a solitary indi- 

 vidual. These divergent branches of organic life 

 may be distinguished in the following manner : 

 An individual may be either unicellular or mul- 

 ticellular. Every cell capable of sustaining life 

 and reproducing its own kind is an individual. 1 



In the case of multicellular individuals there is 

 an unbroken physiological continuity, while life 

 lasts, between the cells of which they are com- 

 posed. All these units spring from one primary 

 cell (i.e. a fertilized egg) which sprang itself from 

 two cells (male and female), proceeding usually 

 from two separate individuals. From the moment 

 that this union is effected, the continuity remains 

 unbroken. 2 When such an individual reproduces 



1 We regard the cell as the unit of life, although, according to 

 Altmann, the unit of life is a still simpler structure the bioblast. 

 He maintains that the bioblast, or living granule, is the ultimate 

 element of the cell ; it is born from a pre-existing granule ; it 

 lives, feeds, reproduces, and is, in fact, an organism (see Die 

 Elementarorganismen und ihre Beziehungen zu den Zellen ; 

 Leipzig, 189Q.~Studien Uber die Zellen; Leipzig, 1886. Zur 

 Geschichte 'der Zelltheorien ; Leipzig, 1889 (Altmann). The 

 existence, however, of the bioblast is a pure hypothesis, no 

 definite proof having been established of its existence ; and to 

 assume that it is the simplest unit of life is to abandon oneself 

 to pure imagination. 



2 Although this theory is in agreement with the observed facts 

 of biology, it is necessary to point out the complexity of the 

 ideas of individual and organism. Boveri (Uber die Bcfruclriungs 



