112 THE AMERICAN NATURALIST [Vol. L 



as homogeneous with greater approach to accuracy than in 

 the case of any other living organism, but it is clear that 

 no living body that is carrying on constructive and de- 

 structive metabolism could remain for a moment perfectly 

 homogeneous or constant in chemical composition. Their 

 bodies were not limited by a rigid envelope or capsule. 

 Reproduction was affected by binary fission, the body di- 

 viding into two with a dumbbell-shaped figure. Their 

 mode of life was vegetative, that is to say, they reacted 

 upon their environmental medium by means of ferments 

 secreted by their own body-substance. The earliest forms 

 must have possessed the power of building up their pro- 

 tein-molecules from the simplest inorganic compounds; 

 but different types of biococci, characterized each by spe- 

 cific reactions and idiosyncrasies, must have become dif- 

 ferentiated very rapidly in the process of evolution and 

 adaptation to divergent conditions of life. 



Consideration of the existing types and forms of living 

 organisms shows that from the primitive biococcal type 

 the evolution of living things must have diverged in at 

 least two principal directions. Two new types of or- 

 ganisms arose, one of which continued to specialize fur- 

 ther in the vegetative mode of life, in all its innumerable 

 variations, characteristic of the biococci, while the other 

 type developed an entirely new habit of life, namely a 

 predatory existence. I will consider these two types sep- 

 arately. 



(1) In the vegetative type the first step was that the 

 body became surrounded by a rigid envelope. Thus came 

 into existence the bacterial type of organism, the simplest 

 form of which would be a Micrococcus, a minute globule 

 of chromatin surrounded by a firm envelope. From this 

 familiar type an infinity of forms arises by processes of 

 divergent evolution and adaptation. With increase in 

 size of the body the number of chromatin-grains within 

 the envelope increase in number, and are then seen to be 

 imbedded in a ground-substance which is similar to cyto- 

 plasm, apparently, and may contain non-chromatinic en- 



