POLYMASTIGINA 



6i 



Body roughly egg-shaped ; with four flagella, of which one is directed 

 backward and united to the body by an undulating membrane ; a cyto- 

 stomenear the broad anterior end ; and an axostyle which projects from 

 the posterior end. The united basal granules act as a division centre, 

 possibly in virtue of a centriole concealed among them. The cytostome 

 is used for ingestion. A staining body which follows the base of the 

 undulating membrane has been regarded as the parabasal body, but 

 a deeper-lying structure is now asserted to represent that organ. In 

 the cytoplasm, a number of ''chromatic granules" are also present. 



Fig. 51. Giardia intestinalis, from the intestine of man. Semidiagrammatic. 

 axs. axostyle (axoneme) ; ba.gr. basal granules; ce. centriole; cone, ventral con- 

 cavity (" sucker ");j^. fibre around concavity; fl., fl.' , fl.", fl.'" anterolateral, 

 posterolateral, ventral, and caudal flagella; kar. karyosome; la.sd. lateral 

 shield, the thickest part of the body; nu. nucleus; p. by. parabasal body; 

 rh. rhizoplasts. 



Several species, parasitic in various cavities of vertebrates, including 

 the mouth, intestine, and vagina of man. 



Hexamitus {=OctomituSj Fig. 4). (Diplomonadina.) Body elon- 

 gate ; without gullet ; presenting strong bilateral symmetry ; and bearing 

 on each side four flagella, three anterior and one posterior, the basal 

 granules of the foremost being united ; and an axostyle. Two nuclei are 

 present, one on each side of the body, near the anterior group of basal 

 granules, with which they are connected. Intestinal parasites of 

 vertebrates. 



