Bacteria 27 



as the knowledge of the organisms themselves is in no particular 

 diminished by the method of classifying them. 



In discussing the matter Delage says, "The question is not so 

 important as it appears. From one point of view and on purely 

 theoretic grounds it does not exist, while from another standpoint 

 it is insoluble. If one be asked to divide living things into two 

 distinct groups, of which one contains only animals and the other 

 only plants, the question is meaningless, for plants and animals are 

 concepts which have no objective reality, and in nature they are only 

 individuals. If in considering those forms which we regard as true 

 animals and plants we look for their phylogenetic history and decide 

 to place all of their allies in one or the other group, we are sure to 

 reach no result; such attempts have always been fruitless." 



"Huxley pointed out as early as 1876 the extremely close relation- 

 ship between the lowest algae and some of the flagellates, and it is 

 the general opinion that no one feature separates the lowest plants 

 from the lowest animals, and the difficulty in many cases the 

 impossibility of distinguishing between them is clearly recognized. 



"The point of view which demands a strict separation of animals 

 and plants has, however, little utility save, perhaps, to determine 

 the limits of a text-book or a monograph."* 



The relative position of the pathogenic vegetable micro-organisms 

 to the other vegetable organisms can be determined by reference to 

 the following table. The wide separation of the bacteria in Group 

 II. and all of the others, which appear in Group X., should be noted. 



The various genera to which the pathogenic fungi belong are by 

 no means closely related to one another, as can at once be seen by the 

 following amplification of Group X. Eumycetes: 



No entirely satisfactory grouping of the bacteria themselves 

 has yet been achieved, the best characters to be used as the basis of 

 classification being undecided. The best system for their provi- - 

 sional arrangement is probably that of Migula,| or the modification 

 of it suggested by F. D. Chester, J in which the morphology, sporula- 

 tion, and appendages of the bacteria all enter as important features. 



Size. Bacteria are so minute that a special unit has been adopted 

 for their measurement. This is the micron, micromillimeter or 

 /*, and is the one-thousandth part of a millimeter, equivalent to the 

 one- twenty-five- thousandth (J^sooo) of an inch. 



There is no limit to the minuteness of micro-organisms. Visibility 

 is no longer a criterion. There are micro-organisms that can be 

 seen with low powers, others that can only be seen with high 

 powers, and a few that probably cannot be seen with any power of 



* Calkins', "The Protozoa," p. 23. 



t" System der Bakterien," Jena, 1897-1900 (vols. i and n appearing at 

 different times). 



J "Preliminary Arrangement of the Species of the Genus Bacterium," "Ninth 

 Annual Report of the Delaware College Agricultural Experiment Station," 

 1897, Newark, Delaware, U. S. A. 



