148 EVOLUTIONISTS OF THE EIGHTEENTH CENTURY. 



ial Creation ; he meets this by establishing his 

 hypothesis upon a basis of natural causation or 

 secondary causes, and says : 



" For if we may compare infinities, it would seem to require a 

 greater infinity or power to cause the causes of effects, than to 

 cause the effects themselves ; that is, to establish the laws of Cre- 

 ation rather than to directly create." 



There are many single passages which further 

 illustrate Darwin's ideas. It is first, perfectly clear 

 that he derives all forms of life from a single fila- 

 ment, which we may translate into a single proto- 

 plasmic mass. Upon this, however, he does not 

 build a branching or phyletic system of Evolution, 

 but simply leaves this part of the system out, and 

 passes on to illustrations of the causes and laws of 

 Evolution. As pointed out above, his fundamental 

 idea is what has since been called ' Archaesthetism ' 

 by Cope. According to this, growth is stimulated 

 by irritability and sensibility, or in Darwin's lan- 

 guage in the passage upwards from the original 

 filament: " The most essential parts of the system 

 are first formed by the irritations (of hunger, thirst, 

 etc., above mentioned) and by the pleasurable sen- 

 sations attending those irritations, and by exertions 

 in consequence of painful sensations, similar to 

 those of hunger and suffocation. ... In confir- 

 mation of these ideas, it may be observed that all 

 parts of the body endeavour to grow or to make 

 additional parts of themselves throughout our lives." 

 (Zoonomia, XXXIX. 3.) 



