1S2 



rROTOZOA 



contractile vacuole are usually lacking (figs. 138, 130, 140. 141) • 

 There are usually one or two llagella at the anterior end; when more 

 occur (eight or move) they are distrihuled over the body. They difler 

 in form and function so that chief, accessory and trailing llagella 

 are distinguished. In the parasitic species there is usually a duality 

 of the nucleus, recalling that of the Infusoria, there being, besides the 

 principal nucleus, a second, the hlcpharophisl, at the base of the llagellum 

 (lig. I v"^, (). The surface of the body is frequently naked, and then is often 

 capaljlc of anuclioid motions. Again it may be covered with a more or less 



evident cuticle. Closed gelatinous en- 

 velopes or open, goblet-shaped cups 

 [loricir, tig. 135) are common. There 

 may also be slender stalks, to which 

 he animals are attached in small groups 

 (fig. 130). 



There are great differences in the 

 feeding and in the organs connected 

 therewith. ]Many feed like animals, 

 taking solid food with pseudopoiha like 

 the Rhi/.opotla or with a mouth like the 

 Infusoria. In the Choanollagellata (lig. 

 136) tlrere is a collar, a funnel-like 

 process of the body protoplasm around 

 the flagellum, to which foreign particles 

 thrown by the fiagellum adhere and are 

 conveyed to the interior. Besides these animal forms are plant-like 

 species which contain cHorophyl (V'olvocina-, liuglenida^) or l)rown 

 chromatophores (Chromomonadinea-), aiding in assimilation and ena- 

 bling the organism to produce paramylum or even starch. It is note- 

 worthy that vegetable ami animal methods of nourishment appear in 

 forms closely related anatomically. Indeed, there are species which 

 possess a cytostome without taking solid nourishment, assimilating 1iy 

 means of chlorophyl or living on Ihiid food (fig. 137). All this shows 

 that the I'iagellata ha\e relations with Rhizopoda, Infusoria, and the 

 lower plants (bacteria and alga-). 



Fig. 13S. — Trypaiiosoina Irwisi 

 (after I^a\'eran el !Mesnil). a, ai;- 

 glomerale; /), single one enlarged; 

 g, flagellum; 11, nucleus; c, blephar- 

 oplast. 



Reproduction is nearly always by fission. Conjugalion is known in many 

 species. In the Volvocina two individuals fuse coniplelcly to form a resting 

 spore. In the colonial Volvo.x globalor the conjugating individuals are unequal, 

 some animals of the colony growing to large immobile oospheres (niacrogametes), 

 while others by division form groups of minute active zoosjiores (microga metes). 

 When fertilized bv the zoos]iore the oospheres fall to the bottom, encyst, and 

 enter a resting stage before they form a new colony. Young colonies reproduce 



