S4 IOWA ACADEMY OF SCIENCES. 



Third. — Katabolism, which would cause the cell to disappear, 

 or anabolism would recur at a certain point, and we would thus 

 have an alternation or rhythm of katabolic and anabolic states. 



This is logically conceivable, but it would debar the possibil- 

 ity of reproduction, and the individual cell would be theoret- 

 ically immortal, but as a matter of fact would be destroyed 

 ultimately by accidental means. 



If, when the cell had reached the limit of size, it should 

 divide, either accidentally or otherwise, there would result two 

 individuals, both small enough to admit of an expression of 

 anabolism in growth. 



There would thus be two organisms to hold the fact of spe- 

 cific existence instead of one. 



Therefore, any cell which would divide would have double 

 the chance of perpetuation that a single cell would. 



In other words, cells capable of spontaneous or mechanical 

 fission would be selected and preserved by natural selection. 



Let 1,000 generations proceed thus by simple division or 

 fission. By this time considerable differences would exhibit 

 themselves in the descendants of our original cell, owing to dif- 

 ferences in environment and food supply. 



One line of cells would be abundantly fed, would grow large, 

 inactive, anabolic. Another line would be insufficiently nour- 

 ished, and would grow smaller, more active, katabolic. 



Taking the large anabolic cells, we find: 



First. — They tend to become more and more inactive. (Activ- 

 ity may express itself either in motion or cell division.) 



Second — The anabolic cells accordingly tend to become quies- 

 cent on the one hand, and to cease dividing on the other. 



Third. — This tendency would ultimately result in death, if 

 not in some way counteracted. 



Taking the smaller katabolic cells, we find: 



First. — They tend to decrease in size. 



Second. — They tend to become more and more active. 



Third — Their expenditures would eventually bankrupt them, 

 they would be worn out, would die of exhaustion. 



Taking the two kinds of cells we find: 



First. — One needs something that can express itself in cell 

 division, Katabolism. 



Second. — The other needs nourishment which would express 

 itself in growth, Anabolism. 



