Chromatin as ^'Hereditary Sub.stance^* 3»3i3 



term centrosome oiipjht to be used in tlie original sense, tlie name 

 ceiitriole^ used by Heidenliain and others for tlie eentral granule, 

 being favored by Hertwig. 



Heidenliain's statement that the centrosome ])r()blem lias re- 

 cently entered a new stage, largely, according to him, through 

 the researches of Vejdo\'sky and Mrazek, seems justified by the 

 observations. "Evidently," says Heidenliain, "in the eentrosomcs 

 of large cells (eggs, blastomcres,) we have to do not with any 

 sort of sharply differentiated bodies of definite organization, not 

 with organs wljose capability rests upon a definite, intrinsic con- 

 stitution reached through systematic development, but with stiN<- 

 tural material transported from ])laee to place through the ac- 

 tivity of the radially differentiated cell substance and heaped up 

 for further use." ^ 



One can hardly avoid reflecting that this statement by Mcid- 

 enhain seems to accord much better witli the ])livsical-clieiiiistrv 

 conception of the cell, that is, with that of the cell as a system 

 of phases in dynamic equilibrium, tlian with the older idea of the 

 centrosome as in some peculiar way a "dynamic center" of the 

 cell. Nevertheless for the ])urpose of a general discussion like 

 that in which we are engaged, we may leave the question of wliat 

 the term centrosome ought to be applied to undecided, and fix 

 attention upon the central granule as belonging structurally to 

 the "cellular center," this phrase being understood to cover a 

 very wide range of objects none of which are simple and some 

 of which are quite complex. 



As to the function of these "centers" there a|)j)ears to be 

 unanimity among the authorities that they are in some way 

 "dynamic centers of the cell" as originally exjiressed by Boveri. 

 There is some satisfaction in tliis unanimity even thniigh the 

 range of possibility in "dynamic" is so wide as to make the 

 unanimity ratlier indefinite. For one thing, it is certain that 

 the centers take an active and important ))art in indirect cell 

 division. This is a basal tenet of modern teachings concerning 

 cell division. The role of the centers as force- and activity- 

 producers which concerns us here is in connection with flagella 

 and movements characteristic of these organs. 



Evidence from the Speruiatozomi. 



There appears to be nearly complete agreement among 

 authorities that the axial filament of the tail of the spernia- 



