THE EVOLUTION PROCESS 243 



essential sex organ, female or male (prepon- 

 deratingly anabolic or katabolic) as the case 

 may be. And as the natural variations and 

 divergencies of plants may be most con- 

 veniently summed in terms of vegetative and 

 floral preponderance respectively, so those of 

 animals similarly fall into the broadly recog- 

 nizable contrast of passive and active, seden- 

 tary and errant, perpetually renewing itself 

 in every group. Hence the contrast of fixed 

 anemone or coral and swimming 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 barnacle and active shrimp, 

 of sluggish beetle and nimble gnat; or again 

 within the same orders, as moth and butterfly 

 always the same dichotomy of passive and 

 active. Here essentially lies the secret of the 

 divergence between ascidian and vertebrate, 

 to take a great difference, or that between 

 toad and frog for a small one; or again this 

 is the main contrast between reptile and bird, 

 Diplodocus and swallow. This lies within the 

 perpetual ^differentiation of these, witness, 

 among reptiles, the sluggish and often colossal 

 tortoises, yet the active and supple snakes; 

 and these (of course) again differentiating 



