272 



THE PROTOZOA 



organism rather than as distinct generic types. Trichomonas hominis is 

 ontozoic in the human intestine, T. vaginalis in the human vagina ; they 

 appear to be harmless scavengers rather than parasites. The encystment 

 of Trichomonas has been the subject of some controversy. According to 

 Alexeieff (326), the supposed cysts of Trichomonas described by various 

 authors are in reality independent vegetable organisms, of the nature 



of yeasts. In some species of Trichomonas the 

 anterior flagella are four in number (Alexeieff, 

 323) ; for such forms Parisi (A.P.K., xix., 

 p. 232) has founded a subgenus Tetratricho- 

 monas. The genus Macrostoma, according to 

 Wenyon (362), differs from Trichomonas in 

 having the undulating membrane wedged in 

 a deep groove ; M. mesnili occurs in the 

 human intestine. According to Alexeieff (324), 

 Macrostoma is a synonym of Tetramitus. Mono- 

 cercomonas, including a number of common 

 intestinal parasites, has four anterior flagella 

 of equal length, or two longer, two shorter 

 (Alexeieff, 325). 



Costia necatrix, also referred to this family, 

 is ectoparasitic on the skin of fishes. According 

 to Moroff, it has four flagella in two pairs, two 

 larger and two smaller, all of which serve for 

 locomotion ; but the larger pair are used also 

 for fixation, and the smaller pair for wafting 

 into the mouth the food-particles, which consist 

 chiefly of dead epithelial cells torn away from 

 the epidermis (see also Neresheimer). 



2. Octomitidce.* With six or eight flagella, 

 arranged in pairs ; the body is bilaterally 

 symmetrical in structure. Entozoic forms, for 

 the most part of intestinal habitat. 

 FIG. 116. Octomitus dujar- The remarkable bilateral symmetry of the 

 dini. W. 1 , Anterior blep- species of this family is not merely an external 

 haroplast, from which the characteristic of the body, but affects the 

 first and second flagella of internal structure as well, and the entire 

 that side of the body arise ; nuclear structure is doubled, with right and left 

 U. 2 , second blepharoplast, halves. Octomitus (synonym, Hexamitus ; see 

 giving off the flagellum of p o bell, 236), with four pairs of flagella (Fig. 116), 

 the third pair ;.#., left-hand indues a number of entozoic species e.g., 

 ?7^ cl !?lL a ?r t axost / 1( 0. intestinalis, from the cloaca of the frog and 



' ^ f P T aS * other animals. Lamblia intestinalis (synonym, 

 the extremity of the axo- ,.. . uc ii\ 



style, giving off one of the Megastoma entencum, Fig. 117) is a common 

 flagella of the fourth pair, inhabitant of the human intestine. It becomes 

 All the structures indicated encysted, and is probably disseminated in this 

 are paired, and the letters form. Within the cyst it divides into two 

 indicate the member of each (Rodenwaldt). L. sanguinis, described by 

 pair on the left side of the Gonder (A.P.K., xxi., p. 209) from the blood 

 body. After Dobell (236). o f a falcon, is probably an intestinal parasite 



gone astray (vide p. 258). 



The order Polymastigina differs little from the Protomonadina except in 

 the complication of the flagellar apparatus, correlated probably with the 

 entozoic habit. Hartmann and Chagas propose to merge the Polymastigina 



* Doflein terms this family the Polymastigidce, but the name is clearly in- 

 admissible, since the genus Polymastix belongs to the preceding family, and is 

 closely allied to Trichomonas, but has six anterior flagella and no trailing 

 flagellum (compare Alexeieff, 325). 



