SOME UNSOLVED SCIENTIFIC PROBLEMS 



within the cell are or are not typical structures, " capa- 

 ble of assimilation, growth, and division, and hence to 

 be regarded as elementary units of structure standing 

 between the cell and the ultimate molecules of living 

 matter." The more philosophical thinkers, like Spencer, 

 Darwin, Haeckel, Michael Foster, August Weismann, 

 and many others, believe that such "intermediate units 

 must exist, whether or not the microscope reveals them 

 to view. Weismann, who has most fully elaborated a 

 hypothetical scheme of the relations of the intracellular 

 units, identifies the larger of these units not with the 

 ordinary granules of the cell, but with a remarkable 

 structure called chromatin, which becomes aggregated 

 within the cell nucleus at the time of cellular division 

 a structure which divides into definite parts, and goes 

 through some most suggestive manoeuvres in the 

 process of cell multiplication. All these are puzzling 

 structures; and there is another minute body within 

 the cell, called the centrosome, that is quite as much 

 so. This structure, discovered by Van Beneden, has 

 been regarded as essential to cell division, yet some 

 recent botanical studies seem to show that sometimes 

 it is altogether wanting in a dividing cell. 



In a word, the architecture of the cell has been shown 

 by modern researches to be wonderfully complicated, but 

 the accumulating researches are just at a point where 

 much is obscure about many of the observed phenomena. 

 The immediate future seems full of promise of advances 

 upon present understanding of cell processes. But for 

 the moment it remains for us, as for preceding genera- 

 tions, about the most incomprehensible, scientifically 

 speaking, of observed phenomena, that a single micro- 

 scopic egg cell should contain within its substance all 



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