214 THE STORY OF LIFE'S MECHANISM. 



quate to the building of machines as well as forces 

 adequate to the formation of chemical compounds 

 and worlds. 



But here again we are unable to base our 

 explanation upon chemical and physical forces. 

 Reproduction, heredity, and variation are pro- 

 perties of the cell machine, and we are therefore 

 thrown back upon the necessity of explaining the 

 origin of this machine. Can we find a mechanical 

 or chemical explanation of the origin of proto- 

 plasm? A chemical explanation of the cell is 

 impossible, since it is not a chemical compound, 

 but a piece of mechanism. The explanation given 

 for the origin of animals and plants is also here 

 apparently impossible. The factors upon which 

 that explanation depended are factors of this 

 completed machine itself, and can not be used to 

 explain its origin. We are left at present there- 

 fore without any foundation for further advance. 

 The cells must have had a history of construc- 

 tion, but we do not as yet conceive any forces 

 which may be looked upon as contributing to 

 that history. Whether life phenomena can be 

 manifested by any mixture of compounds sim- 

 pler than the cell we do not yet know. 



The great problems still remaining for solu- 

 tion, which have hardly been touched by modern 

 biology in all its endeavours to find a mechanical 

 explanation of the living machine, are, therefore, 

 three. First, the relation of mentality to the 

 general phenomena of the correlation of force; 

 second, the intelligible understanding of the 

 mechanism of protoplasm which enables it to 

 guide the blind chemical and physical forces of 



