202 THE STORY OF LIFE'S MECHANISM. 



variation, and heredity are the properties of all 

 living matter ; but they are not, like gravity and 

 chemism, universal forces of nature. They occur 

 in living organisms only. Why should they 

 occur in living organisms, and here alone 1 These 

 three properties are perhaps the most marvellous 

 properties of nature; and surely we have not 

 finished our task if we have based the whole pro- 

 cess of machine building upon these mysterious 

 phenomena, leaving them unintelligible. We must 

 therefore now ask whether we can proceed any 

 farther and find any explanation of these funda- 

 mental powers of the living machine. 



It must be confessed that here we are at present 

 forced to stop. We can proceed no further with 

 any certainty, or even probability. We may say 

 that variation and heredity are only phases of re- 

 production, and reproduction is a property of the 

 living cell. We may say that this power of re- 

 production is dependent upon the power of assi- 

 milation and growth, for cell division is a result 

 of cell growth. We may further say that growth 

 and assimilation are chemical processes resulting 

 from the oxidation of food, and that thus all of 

 these processes are to be reduced to chemical 

 forces. In this way we may seem to have a 

 chemical foundation for life phenomena. But 

 clearly this is far from satisfactory. In the first 

 place, it utterly fails to explain why the living 

 cell has these properties, while no other body pos- 

 sesses them, nor why they are possessed by living 

 protoplasms alone, ceasing instantly with death. 

 Indeed, it does not tell us what death can be. 

 Secondly, it utterly fails to explain the marvels 



