376 SCIENCE PROGRESS. 



the Amoeba just described, the substance of the body may 

 be in constant movement. 



The Amoeba seen creeping in the form of an extended 

 club towards the source of nourishment affords an answer to 

 the question of how it is possible to have permanent shape 

 of the organism where there is active movement of its 

 particles. Given unchanging outward conditions, the iorm 

 depends wholly on the unchanging character and direction 

 of the metabolism. In a fountain or a gas jet, although the 

 particles are in constant movement, not one of them re- 

 taining the same position for a moment, the entire jet 

 retains its characteristic form as long as it is subject to the 

 same conditions. The same is the case with living matter. 

 A cell, in spite of its active metabolism, appears to us to be 

 in repose. It gives us the impression of immovability, just 

 as a gas or water jet conveys that impression although 

 each particle is in rapid and incessant movement. 



This view of the relation between metabolism and form 

 gains an additional interest when applied to the phenomena 

 of development. It is evident that if the metabolism of a 

 cell is continually changing, the changes will find expression 

 in the form of the organism, so long as this is not prevented 

 by factors operating outside the organism. In this way, 

 development is brought about. We know that the meta- 

 bolism of the egg cell is from the first continually changing. 

 The supplies of reserve nourishment are consumed and 

 other matter appears in the cell and in its descendants. 

 Here we have a marked example of the close connection 

 between metabolism and chanore of form. 



In this connection I would protest against the very 

 wide-spread opinion that the Qgo;, cell, especially in the higher 

 animals, must have a highly complicated molecular structure, 

 much more complicated than that of any other cell. This 

 appears to me to be an absolutely groundless assump- 

 tion, recalling the so-called " Einschachtelung Theorie ". 

 Because a highly complicated organism develops from the 

 microscopical egg cell, it is thought that the molecular 

 structure of the latter must be highly complicated. I do 

 not doubt that it is complicated, but I deny the assumption 



