vi PREFATORY NOTE. 



tracted from what remains to be done, the objection has no 

 foundation, for there is no less, and perhaps there is more, 

 mechanism in predetermination than in postdetermination. 

 We may find it difficult to untie the knot of predetermination, 

 or preformation in the sense of preexisting germs, but are we 

 any wiser for the short-cut of denial ? Is our, field of explora- 

 tion reduced by the discovery that germs arise by division of 

 preexisting germs ? Does any one feel it a deprivation that he 

 no longer need search for spontaneous generation among 

 internal parasites ? If so, he could still search. It is a 

 strange perversion of fact to imagine that investigation is 

 obstructed by assuming the egg to be more than a molecular 

 aggregate ; for it is abundantly evident that the expectation of 

 something more has been a powerful stimulus to recent dis- 

 coveries in cytology. Were it possible to remove the grounds 

 of expectation, of course the search would come to an end. 



The search for ultimate units of organization in the ^gg — 

 that is, smallest elements capable of organic growth and 

 self-division — has already led directly to the discovery of 

 mechanism, where molecular epigenetics had disputed it. The 

 molecule is no doubt universal and very mighty, only perhaps 

 not quite almighty. It is quite conceivable that there should 

 be something at least as far above the molecule as the molecule 

 is above the atom. Indeed there seems to be a considerable 

 number of units actually visible in the cell, which are certainly 

 quite as real as the molecule, and which differ from it in having 

 those fundamental attributes of growth and self-division which 

 appear to be peculiar to every grade of organic life. Every 

 such unit may be reducible by chemical disintegration to mole- 

 cules, but we should hardly accept that as proof that no organi- 

 zation above molecules preceded the dissolution. There is no 

 warrant for the assertion that life is something different from, 

 and independent of, matter and energy. That is the mistake 

 of vitalism. On the other hand, there is no warrant in decom- 

 position for identifying dead mechanism with living mechanism. 



The resolution of organs into tissues, tissues into cells, and 

 cells into smaller units, does not disclose the secret of life, but 

 it does extend our knowledge of organic mechanism. It is 



