DOMAIN OF EVOLUTIONAKY HYPOTHESIS 87 



which we so far know the cells whether they be indi- 

 vidual and independently existing beings (monocellular), 

 or constituents of a so-called ' higher ' organism. Since 

 for the first time Briicke (1861) has demonstrated the 

 ultimate morphological and physiological units of which 

 the organs in animals and plants consist viz. the ( cells ' 

 to be an aggregation of varied kinds of parts connected 

 together by definite laws, the organic cells have also 

 been designated as organisms elementary organisms. 



This term is very unhappily chosen, since a liver 

 cell or a kidney cell cannot be termed an ( organism ' 

 in the sense of an independently existing and active 

 whole. 1 Since, however, the expression has become 

 widely spread, and used especially by most of the 

 defenders of spontaneous generation (Urzeugung), we will 

 accept it for the time being. It is important for us to 

 remember that the cell that is, the absolute or relative 

 ultimate unit of living matter itself is composed of 

 many varied elemental parts which, like the organs in 

 a higher organism, co-operate in the vital process. 3 

 If, therefore precisely because the cell consists of 

 many varied and co-operating parts it has been termed 

 an organism, that then is a proof that our definition is 

 accepted by the biology of to-day. We can, therefore, 

 proceed upon that basis. 



In the definition of ' life ' we spoke of the ' definite 

 co-operation of all the parts determined by constant 



1 See E. Wasmann : Die moderne Biologic und die Entwcklungsffieoric; 

 p. 190. 



2 O. Hertwig : Attgemeine Biologie, II. 



