1 60 The Evolution Hypothesis. 



In this way Mr. Spencer reaches actions " called 

 vital." How out of these minute fragments of protein 

 have special kinds of organisms arisen ? 



" Molecules, perhaps, exceeding in size and com- 

 plexity those of protein, as those of protein exceed 

 those of inorganic matter, may, I conceive, be the 

 special units belonging to special kinds of organisms, 

 .... The existence of such physiological units, pecu- 

 liar to each species of organism, is not unaccounted 

 for. They are evolved simultaneously with the 

 evolution of the organism they compose : they dif- 

 ferentiate as fast as the organisms differentiate ; 

 and are made multitudinous in kind by the same 

 actions which make the organisms they compose 



multitudinous in kind Every physicist 



will endorse the proposition, that in each aggregate 

 there tends to establish itself an equilibrium between 

 the forces exercised by all the units upon each and 



by each upon all Organic molecules of each 



kind, no matter how complex, have a form of equili- 

 brium in which, when they aggregate, their complex 

 forces are balanced. . . . The special molecules having a 

 special organic structure as their form of equilibrium 

 must be reacted upon by the total forces of the 



organic structure Setting out with the stage 



in which protein in minute aggregates took on those 

 simplest differentiations which fitted it for differently 

 conditioned parts of its medium, there must have un- 

 ceasingly gone on perpetual re-adjustments of the 



