CHAPTER VI\ 



CELL-LIFE AND CELL-MULTIPLICATION". 



§ 74rt. The proorress of science is simultaneously towards 

 simplification and towards conii)lication. Analysis siniplilies 

 its conceptions by resolving phenomena into their fa(.'t()rs, 

 and by then showing how each simple mode of action may 

 be traced under multitudinous forms; while, at the same 

 time, synthesis shows how each factor, by cooperation with 

 various other factors in countless modes and degrees, pro- 

 duces dilferent results innuni('ral)le in their amounts and 

 varieties. Of course this truth holds alike of processes and 

 of products. Observation and the grouping into classes make 

 it clear that through multitudinous things superficially un- 

 like there run the same cardinal traits of structure; while, 

 along with these major unities, examination discloses innu- 

 merable minor diversities. 



A concomitant truth, or the same truth under another 

 aspect, is that Nature everywhere presents us with complexi- 

 ties within complexities, which go on revealing themselves as 

 we investigate smaller and smaller objects. In a preceding 

 chapter (§§ 54a, 546) it was pointed out that each primitive 

 organism, in common with each of the units out of which 

 the higher and larger organisms are built, was found a gene- 

 ration ago to consist of nucleus, protoplasm, and cell-wall. 

 This general conception of a cell remained for a time the 

 outcome of inquiry; but with the advance of microscopy it 

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