Chromatin as ''Ilcrcditarij Snhsfaucc'' 831 



these plants. That the production of cilia is the main if not 

 the exclusive office of the body in these and other ))lants, \\'( 1)- 

 ber and other observers have made certain. The question of 

 the relation of this body to the centrosonie, which latter is gen- 

 erally held to be part of the nuclear-divisional ap))aratus of the 

 cell^ has been much discussed. In tlie j)lants mentioned Web- 

 ber believed, seemingly with full justification, that the ble))haro- 

 plast arises de novo in the cyto))lasm and at no time has con- 

 nection with any part of the division apjiaratus. It seems to 

 have no office other than that of producing the cilia. Almost 

 certain it is, consequently, that in several distinct groui)s of 

 plants, Ginkgo, cycads and mosses for example, the main ])or- 

 tion of the motile organ of the sperm cell is derived from the 

 cytoplasm of the cell and not from chromatin or any otiier 

 nuclear material. 



But such an origin does not hold for the corresi)onding organ 

 of all sperm cells. In several animals, insects and salamanders 

 for example, there is practical agreement among authorities that 

 the axial filament of the sperm "tail " grows out from the 

 centrosonie." Furthermore, it seems to be acce])ted that in 

 some animals, e.g., some echinoderms and worms, the centro- 

 som.e arises from the nucleus."^ Viewing these facts in connec- 

 tion with the recent tendency to exalt the nucleus as the "seat" 

 of all sorts of cell capacity, and putting them alongside those 

 above sketched concerning the nuclear connection of flagella in 

 some cilia-bearing protozoans, one readily sees the strong teni])- 

 tation to homologize the motor apparatus of the sjicrmatozoan 

 with that of the protozoan and conceive a common basis for both 

 in the nucleus. If the centrosome could be held to have arisen, 

 phylogenetically, from nuclear chromatin; and if the ble])haro- 

 plast, which is unquestionably a cilia-producer, could be counted 

 as fundamentally a centrosomal structure; and could such a 

 generalization be established, it would certainly be a consideral)h' 

 achievement in support of the theory of universal miclear and 

 chromatinic hegemony in development. We must, consecjuently, 

 scrutinize somewhat closely the evidence Mliieh ))()ints in tlnVs 

 direction. 



Evidence from Certain Cells of MuUiccUidar Organisms 



A decade ago the centrosonie prohKni hehl a eoinnianding 

 place in cytological investigation and an extensive litei'a- 



