Evidence from Protozoans 371 



ing with the nuclear apparatus. Tlie elastic axis, arising from 

 the blepliaroplast, can be regarded as a form-determining ele- 

 ment of endoplasmic origin, the sheath as an ectoplasmic motor 

 substance." * 



As this statement illustrates both the factual point with 

 which we are concerned and the perverting influence of elemen- 

 talist theory on supposedly straightforward description, let us 

 examine it. If a flagellum is composed of a core enclosed in 



V 



/--c.p. 



\-ax. 



w 



FIGURE 20. II-AC.DMUM OF EUGLEXA (aFTER BfTSCHLl). 



ax., axial filament, c.p., contractile protoplasm enveloping the axial 

 filament, e.p., end piece of the flagellum. r., root of the flagelluin 

 passing into the liody. 



* 



a sheath, what justification is there for saying that the organ 

 arises from a basal granule ? According to the clear implica- 

 tion contained in the latter part of the statement, only the axial 

 core arises from this source. And if the statement be correct, 

 as it undoubtedly is, that the sheath is ectoplasmic, what occasion 

 is there for throwing into the definition the purely hypothetical 

 notion that the elastic axis is a "form-determining element"? 

 In view of the fact that there is as much observational ground 

 for supposing the sheath to be "form-determining" as there is 

 for supposing the axial core to be so, either both parts should 



