3o6 probIvEm of the: origin of spe:cies. 



primary and all the rest is purely secondary. True enough, man is for his 

 bodily structure entirely dependent upon the metabolic mechanism within 

 him, but I think the mechanism would fare badly for materials for its activity 

 if left to its own devices to supply them. Is it different in the cell ? 



It is wrong, I believe, to hold that either chromatin or plasma is either 

 primary or secondary, because each is absolutely necessary to the other— the 

 chromatin functioning largely in the phenomena of metabolism and growth, 

 the plasma in sensation and motion, and both active in reproduction. The 

 germ plasm we must consider, I believe, to consist of both plasma and chro- 

 matin. Many, on the basis of the phenomena of cell reproduction, will com- 

 bat this idea with the argument — Why is it that the most conspicuous element 

 in reproduction, the chromatin, occupies in this conception a place of minor 

 importance? But have we any basis, other than the tendency of the last 

 twenty years, which has developed methods to render the chromatin conspic- 

 uous, for believing that other elements are not equally im^portant and con- 

 stant? Has any one shown that in cell reproduction there is an unequal or 

 haphazard division of centrosomes, archoplasm, nucleo-plasm, plasma of the 

 asters, and spindle fibers ? These structures are divided with the same impar- 

 tiality between the daughter cells as are the chromosomes. There exists 

 beyond any question a regularly ordered, nearly exact halving of many of the 

 plasmatic structures of the cell in reproduction, and although the daughter 

 cells may differ in size this is always the result of stored foodstuffs; the 

 plasma, especially that concerned in cell reproduction, is shared alike. Our 

 attention has been too much fixed upon the chromatin, which, because of easy 

 demonstration and nicety of results, has blinded us to the significance and 

 equal importance of the process of cell reproduction in the plasma. All our 

 available information as to the chromatin activity, the formation of cell 

 products, enzymes, glandular secretions, nutritives contents of ova, and so on, 

 shows chromatin only as a seat of chemical activity, a trophic material, 

 extremely important, to be sure, but not the whole life of the cell. I believe 

 that from the present state of our knowledge we should regard the chromatin 

 material solely as the seat of nutritive processes and growth activity, the 

 plasma, as the seat of motion and sensation, and reproduction, as involving 

 both. At present there exists not one whit of evidence to show that chro- 

 matin is endovv^ed with other metabolic and growth processes. Reproduction 

 seems to and must of sheer necessity concern both, resulting in an equal dis- 

 tribution to the daughter cells of the plasmic and chromatic constituents of the 

 germ plasm. Reproduction is in reality the only process comm.on to the 

 entire cell mass, and in reproduction the activities of the plasma are equal in 

 importance to those in the chromatin. 



The logical outcome of this conception is that the germ plasm, instead of 

 representing a miosaic or colony of vital elem.ents living within a protoplasmic 



