286 The Unity of the Organism 



tions of internal structure. But while Dujardin's greater 

 merit in these respects was undoubted, his lesser merit in 

 describing the internal structure is quite as undoubted, and 

 more vital in that it involved serious practical consequences. 

 The difference in preconception of the two naturalists made 

 Ehrenherg the better practical anatomist of the protozoa. 

 It will have been noted that Dujardin's opposition to Ehren- 

 berg did not primarily involve the question of the applica- 

 tion of the cell-theory to the protozoa, both men having 

 published their main works before that theory was pro- 

 pounded. 



Modern Opposition to the Effort to Make the Protista Con- 

 form to Cellular Element alism 



We noAv pass on in our examination of historical opposi- 

 tion to the conception that unicellular plants and animals 

 are "organisms without organs," into the strictly modern 

 period during which the effort has been to bring the protista 

 "into conformity with the narrow bounds of cellular elemen- 

 talism." 



(«) The Position of Friedrich Stein 



I suppose all protistologists would agree that there has 

 been no greater worker in microscopic natural history dur- 

 ing this period than Friedrich Stein. His Der Organismus 

 der Infusionsthiere (nach eigenen Forschungen) is no less a 

 fundamental and indispensable part of the library of every 

 student in this field than is Ehrenberg's great work. That 

 Stein "was never an ardent advocate of the simplicity of the 

 Protozoa," as Calkins expresses it, is well known to all 

 zoologists acquainted with his writings. Both Calkins and 

 Dobell quote the following sentence from him, which not only 

 shows his skepticism about the unrestrained applicability of 

 tlic cell-theory to the protozoa, but indicates the sort of 



