S96 The Unity of the Organism 



selves. It was the appreciation of the significance of this 

 fact that made the theory seem to Huxley wholly inap- 

 plicable to the protozoa. "How,'' he said, "imagine struc- 

 tures which are professedly only elements in the make-up 

 of one kind of organisms, to be the same as structures which 

 are the whole organism in other kinds of beings .f^" This 

 same difficulty seems to have been the chief influence in lead- 

 ing Dobell to deny that the Protista can be legitimately 

 brought under the cell-theory. 



I wish to point out that while there can be no doubt 

 about the great importance of the fact that in metazoa and 

 metaphyta cells are parts of the organisms, I am unable to 

 see that the fact necessitates, as held by Huxley and Dobell, 

 the exclusion of protozoa from the cell-theory. It simply 

 establishes in the most uncompromising way the subordina- 

 tion of the cells to the organism in the metazoa and meta- 

 phyta. If the idea be grasped that cells are among the in- 

 strumentalities produced by organisms in the course of their 

 development, individual and racial, with which to carry on 

 their various activities, it will become apparent that there 

 can be no objection to modifying the conception of the cell 

 to make it apply to any structure whether a part of, or the 

 whole of an organism, which satisfies certain well-established 

 criteria. When, for example, it is recognized that certain 

 species of amoebae resemble so closely the white corpuscles 

 of the blood of many animals as never to fail of recogni- 

 tion by good observers, the established principles of bio- 

 logical definition and classification dictate that the two sorts 

 of bodies be given a common, that is, logically speaking, a 

 generic name. 



But now comes another principle of description and class- 

 ification which, though no less fundamental than that just 

 mentioned, has not been as adequately heeded by defenders 

 of the cell-theory ; the principle, namely, that a genus al- 

 ways implies species and that these must each be as carefully 



