6o 



THE INVERTEBRATA 



plasm to the base of the collar, where they are received by a vacuole 

 which is formed between the cuticle, if present, and the protoplasm 

 (Fig. 49 C) : defaecation within the collar. There is usually a stalk, 

 generally not of living matter. This may branch, and thus unite 

 numerous zooids. Examples are Monosiga (Fig. 49 A), solitary, with 

 protoplasmic stalk ; Codosiga (Fig. 49 B), branched, with cuticular stalk. 



Order POLYMASTIGINA 

 Zoomastigina with two to many, generally with more than three, 

 flagella; and an extranuclear division centre. 



Fig. 50. Trichomonas muris, semidiagrammatic. From Hegner and Talia- 

 ferro, after Wenrich. axs. axostyle; ce. compound basal granule which acts 

 as a centriole; ch.gr. inner row of chromatic granules; ch.gr.' outer row of 

 chromatic granules; ch.rd. chromatic basal rod of undulating membrane; 

 ch.rg. chromatic ring at the emergence of the axostyle; ft. anterior flagella; 

 fl.' posterior flagellum ; kar. karyosome; M. mouth (cytostome) ; tiu. nucleus; 

 p.hy. parabasal body; u.me. undulating membrane; ii.me.' posterior flagellum 

 lying along the edge of the undulating membrane. 



The genera here placed in one order are usually separated as Poly- 

 mastigina, Hypermastigina, and Diplomonadina. They are the most 

 highly organized members of the Mastigophora. 



Trichomonas (Fig. 50). (One of the Polymastigina sensu stricto.) 



