MORPHOLOGY AND TAXONOMY OF MASTIGOPHORA 291 



and lack confirmation. The same is true of the autogamous pro- 

 cesses described for Anfhophi/sa, ProwazekcUa, Bodo and Leptomonas. 



Family 1. Trimastigidse, Pascher and Lemmermann. — Bilater- 

 ally symmetrical forms with one primary and two trailino; flagella. 

 Two genera are included neither of which is adequately described — 

 DaUingeria, Kent, and Macwntasti.v, Stokes. 



Family 2. Bicoecidse.— House-dwelling forms with rudimentary 

 collar, single or colonial (Fig. 139); with (Histiona) or without 

 (Bicosoeca) contractile stalk. 



Family o. Oicomonadidae.— Uniflagellate small forms of oval or 

 elongate shape, freciuently amoeboid. The flagellum is anchored 

 in the body by a simple basal body or by a rhizoplast with basal 

 body. 



Family 4. Trypanosomatidae. — From a practical medical or 

 public hygiene point of view, the Trypanosomatida:" are among the 

 most important of all Protozoa. Several known diseases of man 

 and of domesticated animals are due to them, and other diseases 

 are possible through adaptations of forms which are now commensals 

 or parasitic in lower types of animals. They dift'er from other 

 Protomastigifla in the possession of a well-marked periplast which 

 gives a definite form to the body but still allows plasticity. The 

 form is usually ellipsoidal and pointed at one or at both ends (Fig. 

 4(S, p. 97). Mouth ])arts are absent and nutrition is osmotic. The 

 flagellum is single arising from a basal body which is either inde- 

 pendent of a blepharoplast or united with it, and follows the margin 

 of an undulating membrane to the anterior end of the body where 

 it becomes a free whip. A parabasal body is present in some cases. 

 In Trypanosoma leivisi the developmental cycle in the arthropod 

 intermediate host has been fully worked out by Minchin and 

 Thompson (1915, see Fig. 118, p. 238). 



Family 5. Choanoflagellidse, Stein.— The collared flagellates are 

 small forms (10 ^ to 20 yu) with a single flagellum and with an occa- 

 sional second flagellum which is used for anchoring. The essential 

 characteristic is the possession of a delicate protoplasmic collar, 

 sometimes double, in the form of a funnel surrounding the flagellum 

 (Fig. 18, p. 39). This may be rudimentary in some forms which 

 are here included in the Bicoecida^. They are sedentary forms 

 which, if temporaril\' freed, swim with the flagellum backward. 

 Contractile vacuoles are simple and one or two in number. Nutri- 

 tion is holozoic or saprozoic, and reproduction is by simple di\ision 

 with frequent colony formation. 



Family 6. Phalansteriidse.— These are small forms, also provided 

 with collars, but both collars and cell bodies are embedded in jelly, 

 the flagella alone protruding. Only one genus— Phakuisterium 

 (Fig. 20, p. 41). 



