46 GENERAL ORGANIZATION OF THE PROTOZOA 



Sfirocheta didtoni and in Spirocheta gallinarum. It is not improbable 

 that such diffuse and variable filaments, and with them perhaps the 

 so-called flagella of some bacteria, are mere transitory structures of 

 the cell, which, like the filaments sometimes seen on the outer side of a 

 diatom's shell, owe their origin not to any formed structural element 

 of the cell, but to some unformed exudation of a gelatinous nature, or 

 to disintegration of the cell membrane, or to some other fortuitous 

 cause. ^^Tiatever future research may show them to be, the so-called 

 flagella of these forms are as yet much too indefinite and too uncertain 

 to be taken as a basis for specific differences (see p. 223, and Fig. 88). 

 The various modes of origin of true flagella, as distinguished from 

 these transitory filaments, have recently been studied by Dobell ('08), 

 who makes out four distinct types, as follows: One, in which the 

 flagellum arises directly from the nucleus (cf. axiopodia of actino- 

 phrys or dimorpha); a second, in which the flagellum base is united 

 to the nucleus by a connecting filament, the "zygoplast," as in monas; 

 a third, in which the flagellum arises from a basal granule which is 

 independent of the nucleus, as in copromonas, herpetomonas, etc.; 

 and a fourth, in which the flagellum arises from a special "motor" 

 nucleus, the "kinetonucleus," as in trypanosoma (Fig. 16). 



CLASSIFICATION OF THE MASTIGOPHORA. 



Subphylum. MASTIGOPHORA. Protozoa in which the kinoplasm is concentrated 

 in the form of one or more vibratile or undulating motile processes, called 

 flagella, or in a kinetonucleus which may lie inside or outside of the tropho- 

 nucleus. Simplest forms closely related to bacteria. 



Class 1. ZOOMASTIGOPHORA. Flagellated forms in which animal characteris- 

 tics are predominant. 



Subclass. Lissoflagellata. "Smooth" flagellates, i. e., without protoplasmic 

 collars. 



Order 1. Spirochetida. Organisms, often pathogenic, of somewhat uncertain 

 position because of incomplete knowledge of flagella and life history; spiral 

 in form, the turns of the spiral more or less plastic; nuclei unknown or dis- 

 tributed as in bacteria; division either transverse or longitudinal, sometimes 

 both. 



Typical genera: Spirocheta Ehr., 1S33; (?) Treponema, Schaudinn, 1905; (?) 

 Spiroschaudinnia, Sambon, 1907. 



Order 2. Monadida. Organisms of simple structure, the body being often plastic 

 or even ameboid and with one or more flagella at one end (so-called " anterior" 

 end) ; there is no distinct mouth opening, the food materials being ingested by 

 a soft area of protoplasm at the base of the flagellum; in some cases the 

 organisms are saprozoites. 



Family RMzomasiigidce: Simple organisms with one or two fla£;ella and with an 

 ameboid body capable of forming pseudopodia which may be lobose, as in 

 rhizopods, or axial, as in heliozoa; food taking is assisted by flagellum and 

 pseudopodia. 



Typical genera: Mastigameba, Schultze, 1S75; Dimorpha, Gruber, 1 SSI : Actino- 

 monas, Kent, 1880; Mastigophrys, Frenzel, 1S91. 



