412 



BIOLOGY OF THE PROTOZOA 



sub-phyla treated, while the keys to genera are entirely recast. 

 An important change is the omission here of all groups of chlorophyll- 

 hearing forms. Beginning with Pascher (1914) these were classified 

 as Algae, and they find a much more logical position as branches 

 of the botanical Stammbaum than they have in any protozoan rela- 

 tionship. As Protista or as Protophyta they have their unques- 

 tioned place, but as Protozoa they are anomalous (see also p. IS). 

 Diesing's term Mastigophora referred primarily to plant flagellates 

 and a new term should be provided for animal flagellates; I suggest 

 the sub-phylum Zoomastigophora. 



Fig. 174. — Types of Rhizomastigidae. A, Mastigamoeba aspera. B, Actinomonas 

 mi nihil is; f, flagella; /), pseudopodia. (From Calkins after F. E. Schultze and Sav. 

 Kent.) 



The only common characteristics of this group of Protozoa are 

 the possession of one or more vibratile motile elements in the form 

 of flagella, and reproduction by longitudinal division. In other 

 respects they differ widely in: (a) Complexity of organization, 

 axial relations, symmetry and body form; and (b) distribution and 

 mode of life. 



Organization. — Many of the flagellates are simple ellipsoidal mon- 

 axonic organisms with a single flagellum at the anterior end (Pro- 

 tomonads); others are ameboid (Pantastomatida, Fig. 174); some 

 are bilaterally symmetrical (Diplozoic forms); some spherical 

 (Actinomonas, etc.) and some are spirally twisted (Holomastigo- 

 tidae, etc.). 



While flagella are for the most part all similar in finer structure 



