182 



PROTOZOA 



contractile vacuole are usually lacking (figs. 138, 139, 140, 141). 

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

 occur (eight or more) they are distributed over the body. They differ 

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

 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 blep/iaroplast, at the base of the flagellum 

 (fig. 138, r). The surf ace of the body is frequently naked, and then is often" 

 capable of amoeboid motions. Again it may be covered with a more or less 



evident cuticle. Closed gelatinous en- 

 velopes or open, goblet-shaped cups 

 (loricce, fig. 135) are common. There 

 may also be slender stalks, to which 

 he animals are attached in small groups 



(% 13)- 



There are great differences in the 

 feeding and in the organs connected 

 therewith. Many feed like animals, 

 taking solid food with pseudopodia like 

 the Rhizopoda or with a mouth like the 



Infusoria. In the Choanoflagellata (fig. 

 FIG. 138. Trvpanosoma leivisi 

 (after Laveran et Mesnil). a, ag- I 3) there is a collar, a funnel-like 



glomerate; b, single one enlarged; process of the body protoplasm around 



g, flagellum; n, nucleus; c, blephar- , a .. J r , . 



oplast. the flagellum, to which foreign particles 



thrown by the flagellum adhere and are 



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

 species which contain chlorophyl (Volvocinae, Euglenidze) or brown 

 chromatophores (Chromomonadinese), aiding in assimilation and ena- 

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

 worthy that vegetable and animal methods of nourishment appear in 

 forms closely related anatomically. Indeed, there are species which 

 possess a cytostome without taking solid nourishment, assimilating by 

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

 that the Flagellata have relations with Rhizopoda, Infusoria, and the 

 lower plants (bacteria and alga?). 



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

 In the Volvocina two individuals fuse completely to form a resting 

 spore. In the colonial Volvox globator the conjugating individuals are unequal, 

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

 while others by division form groups of minute active zoospores (microgametes). 

 When fertilized by the zoospore the oospheres fall to the bottom, encyst, and 

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



