i8 AMCEBA 



living protoplasm : these are processes of constructive meta- 

 bolism or anabolism. Next we have the protoplasm gradually 

 breaking down and undergoing conversion into excretory 

 products : this is the process of destructive metabolism or 

 katabolism. There can be little doubt that both are pro- 

 cesses of extreme complexity : it seems probable that 

 after the food is once dissolved there ensues the successive 

 formation of numerous bodies of gradually increasing 

 complexity (anabolic mesostates or anastates\ culminating 

 in protoplasm ; and that the protoplasm, when once formed, 

 is decomposed into a series of substances of gradually 

 diminishing complexity (katabolic mesostates or katastates\ 

 the end of the series being formed by the comparatively 

 simple products of excretion. The granules in the endosarc 

 are probably to be looked upon as various mesostates im- 

 bedded in the protoplasm proper. 



Living protoplasm is thus the most unstable of substances ; 

 it is never precisely the same thing for two consecutive 

 seconds: it "decomposes but to recompose," and recom- 

 poses but to decompose : its existence, like that of a water- 

 fall or a fountain, depends upon the constant flow of matter 

 into it and away from it. 



It follows from what has been said that if the income of 

 an Amoeba, i.e., the total weight of substances taken in (food 

 plus oxygen plus water) is greater than its expenditure or 

 the total weight of substances given out (faeces plus excreta 

 proper plus carbon dioxide) the animacule will grow : if 

 less it will dwindle away : if the two are equal it will 

 remain of the same weight or in a state of physiological 

 equilibrium. 



We see then that the fundamental condition of existence 

 of the individual Amoeba is that it should be able to form 

 new protoplasm out of the food supplied to it. But some- 



