5o THE ANIMAL PARASITES OF MAN 



of flagella, which cross one another, arise in a groove formed by the 

 anterior edge of the sucking disc. Two pairs of flagella (lateral and 

 median) are inserted on the posterior edge of the disc, while the 

 posterior flagella occur at the tapering posterior extremity of the body. 

 Basal granules are found at the bases of the flagella. The median 

 flagella are most active in movement, the anterior and lateral flagella 

 being less motile, as they are partially united to the body for part of 

 their length. 



The nuclear apparatus is situated in the thin, anterior, hollowed 

 part of the body. It is at first dumb-bell shaped, the " handle " of the 

 dumb-bell being formed by a very slight connecting strand, which 

 eventually separates, so that the flagellate becomes binucleate, and thus 

 completes the general bisymmetry of the organism. 



There is a karyosome in each nucleus. Other bodies of unknown 

 function, and possibly composed of chromatin, occur on or near 

 the axostyles. 



FIG. 19. Lamblia inteslinalis. A, ventral view ; B, side view ; N, one of the two nuclei ; 

 ajr., axostyles; y? 1 ,^ 2 ,^? 3 ,^? 4 , the four pairs of flagella ; s, sucker-like depressed area on the 

 ventral surface; x, bodies of unknown function. (After Wenyon.) 



Division has not been observed in the flagellate stages of the 

 Lamblia, but it occurs within the cysts. The resistant cysts (fig. 20, e) 

 are oval and are surrounded by a fairly thick, hyaline cyst wall. 

 They measure 10 //- to 15 //, by 7 /JL to 9 //,, and may be tetranucleate. 

 According to Schaudinn, the cysts arise from the conjugation of two 

 individuals, and nuclear rearrangement occurs. 



