330 THE EVOLUTION THEORY 



It was certainly niatle ovitlent by these experiiiients that In- 

 fusoiians which were prevented from conjugating were incapable 

 of unlimited persistence. But even this in no way proves that 

 amphimixis has a power of rejuvenating life, but simply that these 

 animals are adapted for conjugation, and that they degenerate without 

 it, just as the sperm-cell or the ovum dies if it does not attain to 

 amphimixis. 



My opponents take it as axiomatic that the life-movement mut<t. 

 come to a standstill of itself, and that it therefore requires help. 

 Even so distinguished a specialist on the Protozoa as Butschli argues 

 that organisms are not i)erpetua mohilia, and when one remembers 

 the pln'sicist's theory of the impossibility of a 2^&^T^tuum mohile this 

 looks at first sight like a formidable objection. But does the organism 

 always remain the same as long as it lives, like a pendulum which 

 friction causes to swing more and more slowly till ultimately it comes 

 to a standstill ? We know surely that the phenomena of life arise 

 from a continual process of combustion, which is followed by a constant 

 replacement of the used-up particles by new particles ; we know that 

 life depends on an unceasing metabolism, wdiich brings about changes 

 in the material basis of the organism every moment, so that it is 

 constantly becoming new again. 



I shall attempt to show later on that the cells cannot be the 

 idtimate elements of the organism, but that the life-units visible with 

 the microscope must be made up of smaller invisible units. These, 

 therefore, undergo ' metabolism,' wdiich conditions their multiplication 

 and their destruction, and this ' metabolism ' is not to be seen only in 

 the building up and breaking down of ' albuminoid substances,' as the 

 physiologists say, but in the alternation between the multiplication 

 and the dissolution of these smallest vital particles. Therefore, it 

 seems to me that the movement of life, wdiether in a single-celled or 

 in a many-celled organism, is not to be compared to one pendulum, 

 but to an endless number of pendulums which succeed one another 

 imperceptibly in the course of the metabolism, always producing anew^ 

 the same result, which therefore may continue ad infinitumi. Suppose, 

 then, that w^e possessed our present conception of life as a process of 

 combustion, and of metabolism as the agency which continually 

 provides new combustible material in the shape of new vital particles, 

 but that we knew nothing about multicellular organisms and their 

 transitory existence, but w^ere acquainted only with unicellular 

 organisms and their unlimited multiplication by division. If w^e were 

 then to make the observation that all multicellular organisms are 

 mortal, subject to natural and inevitable death, it w^ould at first 



