GREAT STEPS IN EVOLUTION 95 



It is not merely thai; plants in their stoic- 

 Hirn.1 fp]p.tinng Terr^/jn ft.bout the level of 

 fl.mong n.T)i]rpfl,1s; it is that they 

 entirely different, line of evolution . 



Plants and animals are incommensurable and 

 antithetic. 



If we take a series of sedentary animals, 

 such as zoophytes or alcyonarian corals, we 

 find, as in plants, a wealth of variety within 

 narrow range, an exhausting of the possi- 

 bilities of ramification and colony-making, a 

 great development of hard supporting parts, 

 and many nice adjustments to slight environ- 

 mental peculiarities. They and the plants 

 have a similar kind of beauty expressing the 

 dream-smiles of their sleep-like life. 



How different this is from what we see 

 among the free-living animals which made 

 one important step after another. Keeping 

 to backboneless animals for the moment, let 

 us notice some of the great acquisitions 

 hjjateral symmetry . jjjiead-brain. 



sense-organs, a body-cavitv, a segmented.. 

 body, muscular feet, a^enewahle external . 

 armour. musculay jointed appfip f) ages, and so 

 on. Or let us think of particular cases such 

 as the extraordinary development of the res- 

 piratory system in insects, where ramifying 

 tubes carry air to every nook and cranny of 

 the body, so that the blood can hardly ever 



