242 The Unity of the Orcfanism 



clature wliich starts out by calling the major parts of the 

 body of this organism "plasm," and then names all the de- 

 tails of organization in keeping with this. It would be quite 

 as consistent and quite as useful to call all that part of a 

 fish, for example, situated outside the viscera "extra-vis- 

 ceral plasm/' and then name the skin, bones and muscles 

 "dermoplasm," "osteoplasm," "myoplasm." 



True Organs in Some Protozoans 



But objectionable as is the usual treatment of the term 

 tissue when viewed from the standpoint of a theoretical biol- 

 ogy that is adequate and generous, even more objectionable 

 is the treatment of the term organ. What could be more 

 absurd than to contend that an animal like Diplodinium (see 

 figure 1) has no true organs, while one like Stenostomum, 

 figure 4, has such organs ! No zoologist who becomes so 

 interested in any of the higher protozoa as to nse above the 

 theoretical notions into which he may have been schooled as 

 to what an organ is, hesitates to call many of the parts of 

 these creatures organs. Thus speaking of his discovery of 

 what he regards as functionally a supporting apparatus for 

 the gullet in an infusorian related to Diplodinium, A. Giin- 

 ther says : "I have found an organ lying in the ectoplasm. 

 . . ." ^^ Sharp's excellent description and illustrations of 

 this organ (or these organs, for there are three of them) 

 in Diplodinium, establish its indubitable right to be called 

 an organ. 



Both historically and biologically there are two criteria 

 for an organ. One, the more important, is that a part 

 shall perform a definite office or function in the economy of 

 the organism ; the other, that it shall be composed of definite 

 elements to which usually the term tissues may be applied. 

 As to how the organ in question of Diplodinium measures 

 up to these criteria, we will let Sharp tell us. Concerning the 



