THE EVOLUTION PROCESS 243 



alizes our animal no less than our vegetable 

 classifications. Thus the greatest of all steps 

 in morphological progress, that from the uni- 

 cellular Protozoa to the multicellular Meta- 

 zoa, is plainly not due to the external selec- 

 tion of the more individuated and highly 

 adapted Protozoan species, but is under- 

 stood from within, as the union of relatively 

 embryonic and unindividuated cells into an 

 aggregate in which each becomes diminish- 

 ingly competitive as regards its fellows, and 

 increasingly subordinated to the social whole; 

 while within the body thus developed, a 

 series of cells remains relatively undiffer- 

 entiated as the essential sex organ, female or 

 male (preponderatingly anabolic or katabolic) 

 as the case may be. And as the natural 

 variations and divergences of plants may be 

 most conveniently summed in terms of vege- 

 tative and floral preponderance respectively, 

 so those of animals similarly fall into the 

 broadly recognizable contrast of passive and 

 active, sedentary and errant, perpetually 

 renewing itself in every group. Hence the 

 contrast of fixed anenome or coral and swim- 

 ming jelly-fish or ctenophore, of stony tube- 

 worms and naked creeping or swimming 

 worms, or the contrast, yet series, of fixed 

 crinoid and boring urchin with creeping star- 

 fish and active sand-star; or again of passive 



