390 GREAT STEPS IN ORGANIC EVOLUTION 



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

 hyper-kinetic counterpart. 



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

 evolution, which went on simultaneously with that of the 

 animal world, the two often intersecting, indeed intertwining. 

 Perhaps the most striking general impression is that of a 

 succession of dominant groups, each of great excellence, 

 each attaining a climax and supremacy and then yielding 

 to another. Thus the gigantic Club Mosses and Horsetails 

 of the Carboniferous forests, to which Man owes so much, 

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

 cance, with little more than pigmy representatives to-day; 

 thus the Cycadophytes in their turn yielded to Flowering 

 Plants. 



5. The Making of Bodies. 



It was an epoch-making step in organic evolution when 

 ' bodies ' began to be, that is to say when the transition was 

 made from the unicellular to the multicellular grade of or- 

 ganisation. In some Protozoa the division of the unit is 

 not followed by actual separation, the daughter-units re- 

 main associated instead of drifting apart, and thus, coherent 

 colonies arise. In some such way multicellular organisms 

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

 was primarily important, for many a Rotifer with a thousand 

 cells is smaller than a unicellular Protozoon, such as .the 

 Noctiluca which causes much of the 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 



