202 PROTOZOA. 



Reproduction is nearly always by fission. In many species 

 conjugation is known, best in those plant-like forms, the Volvo- 

 cina, where two individuals fuse completely to a resting spore. In 

 the colonial Volvocina the conjugating individuals are unequal in 

 size, some animals of the colony growing to large immobile 

 oospheres, while others by continued division form groups of 

 minute active zoospores or spermatozoids. When fertilized by 

 the zoospore the oospheres fall to the ground, become encysted, 

 become brown in color, and enter a resting stage before they form 

 a new colony by division. 



Sub Order I. PHYTOFLAGELLATA. Plant-like chlorophyl-bearhig 

 flagellates, mostly with eye-specks. Volvocina : Volvox glohator,* green 

 sphere 0.2-0.7 mm. in diameter, consisting of thousands of individuals 

 which propel the colony by their flagella. Euglenidge : Euglena viridis * 

 (fig. 134), solitary, coloring small pools bright green (a red variety colors 

 them purple) by their immense numbers. Chrysomonadina, plant-like in 

 nourishment but rarely taking solid food : Dinohryon * (fig. 136). 



Sub Order II. CHOANOFLAGELLATA. With collars ; mostly small 

 colonial forms. Codoslga * (tig. 138, B) ; Conodadxum, numerous indi- 

 viduals united on a stalk (fig. 130). 



Sub Order III. EUFLAGELLATA. Animal flagellates, taking solid 

 particles of food either by pseudopodia or by a more or less developed 

 cytostome. Monadina. Here belong, besides numerous free forms, several 

 parasites of man : Lamhlia iCercomonas) intestinalis, fig. 139 {Mega- 



FiG. 139. Fig. UO. 



Fig. Vi^.— Lamhlia intesthuilis. (After Grassi.) Front and side views, i/. nucleus 

 Fig. liO.—Trichomonas vaginalis. (After Blochmann.) », nucleus (fourth flageUuni 

 lacking in figure). 



stoma erUericum); also in rats and mice : Trichoino7ias hominis (T. infes- 

 tiitalis), both in small intestine. T. vaginalis (fig. 140). 



