370 The Unity of the Organism 



(b) What Study of the Ontogeny of Diplodinium Will 



Probably Discover 



Unfortunately^ next to nothing is as yet known about the 

 ontogeny of Diplodinium. Mr. Sharp, who has taught us so 

 much about its adult anatomy, has its development under investi- 

 gation, but until his studies are brought to a conclusion we can 

 do no more than ask questions pertinent to the discussion in hand. 

 Let ns fix attention upon the skeleton and the neuromotor ap- 

 paratus, for example, figure 1 (sk. lam., m. m. and circ. oes. 

 ring). When the origin and growth of these organs come to 

 be studied, judging from our general knowledge of development, 

 what will be observed will be a transformation in one way or 

 another of a portion of the cytoplasm into these parts. Nor is 

 it at all unlikely that, assuming that the work is done with the 

 best technical methods available, chromatic material from the 

 micronuclei will prove to play a part in the differentiation. Does 

 any one suppose that the investigator will be able to prove that 

 the seeming participation of the cytoplasm is a delusion and 

 that the only form-determining agent is the chromatin.^ Yet 

 nothing less, we must insist, will be required to prove the hypo- 

 thesis that chromatin is the hereditary substance in these animals. 



(c) The Origm of Flagella 



When presenting evidence of the direct participation of the 

 nuclear chromatin in the production of organs, we pointed to 

 the growth of the axial filament of the flagellum in certain pro- 

 tozoans as an especially clear case. Now we must inquire about 

 the origin of the other part of the flagellum — for the fact of 

 its having an axial part or core necessarily implies that there is 

 another part. Seemingly it is fully established that the axial 

 core is enclosed in a contractile sheath or envelope as described 

 and figured by Biitschli and others, figure 20. Nor is it 

 questioned apparently, that the envelope is ectoplasmic. Even 

 Minchin. partial as he always is toward chromatin, does not re- 

 fuse to admit this. But his way of describing the flagellum is 

 highly interesting. "A flagellum consists in an elastic axial core 

 enclosed in a contractile sheath or envelope. .... The flag- 

 ellum takes origin from a more or less deeply-seated granule, the 

 blepharoplast, or basal granule, which will be described in deal- 



