Evidence from Protozoans 397 



Concluding Remark on Evidence Presented 



Our objective study of the production of hereditary 

 structures and activities in the protozoa may well end with 

 a comment on a paragraph occurring in one of Calkins' able 

 and useful papers. In the general conclusions of this paper 

 we read: "The chromatin, in addition to being the recog- 

 nized agent in heredity, is also generally recognized as the 

 center of formative changes in the ordinary vegetative ac- 

 tivities of cell life. Recent observations have been inter- 

 preted to show that it is the seat of oxidative processes and 

 the direct agent in metabolism. These various supposed 

 functions of the chromatin are, in large part, inferential, 

 and there are no observations to show whether it alone is 

 the center of these various activities, or whether it plays 

 the part of middleman in the cell. I do not know whether 

 it is possible to determine such a point." 



I ask the reader to note attentively this group of state- 

 ments. According to the opening words chromatin is "the 

 recognized agent in heredity," while according to the last 

 sentence not only is such a role of the chromatin "largely 

 inferential" and there are "no observations to show" that 

 "it alone is the center" of such activity, but the author 

 frankly admits himself in doubt as to the possibility of de- 

 termining such a point. 



What I chiefly wish to do in connection with this is to 

 insist that such facts as we have just been examining, sonic 

 of which were discovered by Calkins himself, relative to the 

 participation of non-chromatic parts of the cell in the 

 ontogeny of many protozoans, are, according to my inter- 

 pretation, conclusive evidence that chromatin is not alone 

 the "center" of activity of hereditary development. For 

 the rest I do no more in this chapter than call attention 

 to the fact that further discussion of the matter at issue is 

 not biological in a strict sense, but is part of the problem 



