390 GREAT STEPS IN ORGANIC EVOLUTION 



kinetic type of man and bis energetic, excitable, rebellious, 

 byper-kinetic counterpart. 



It is beyond our present scope to follow tbe plant line of 

 evolution, whicb went on simultaneously witb tbat of tbe 

 animal world, tbe two often intersecting, indeed intertwining. 

 Perhaps tbe most striking general impression is tbat of a 

 succession of dominant groups, eacb of great excellence, 

 eacb attaining a climax and supremacy and tben yielding 

 to anotber. Tbus the gigantic Club Mosses and Horsetails 

 of tbe Carboniferous forests, to wbicb Man owes so mucb, 

 yielded to Cycad-like forms and passed into relative insignifi- 

 cance, witb little more tban pigmy representatives to-day; 

 tbus tbe Cycadopbytes in tbeir turn yielded to Flowering 

 Plants. 



§ 5. The Making of Bodies, 



It was an epocb-making step in organic evolution wben 

 ^ bodies ' began to be, tbat is to say wben tbe transition was 

 made from tbe unicellular to tbe multicellular grade of or- 

 ganisation. In some Protozoa tbe division of tbe unit is 

 not followed by actual separation, tbe daugbter-units re- 

 main associated instead of drifting apart, and tbus, coherent 

 colonies arise. In some such way multicellular organisms 

 may have been evolved. It was not increase of size tbat 

 was primarily important, for many a Rotifer with a thousand 

 cells is smaller tban a unicellular Protozoon, such as tbe 

 Noctiluca which causes much of tbe phosphorescence of our 

 summer seas. Nor was the step primarily one of increased 

 complexity, either of structure or of activity, for many uni- 

 cellular organisms are far more complex in plasmic and in 

 skeletal architecture and in their behaviour than are, for 

 instance, the fresh-water polyps, built up as these are of 



