298 FAMILY: MONADIDvE 



B. MONADIDiE WITH TWO FLAGELLA. 



Many free-living flagellates provided with two flagella have been 

 described. Such are the various flagellates placed by Stein in the genus 

 Monas. These are minute organisms which occur in stagnant water. 

 They have ovoid or elongate amoeboid bodies and two flagella, the thinner 

 one of which is about twice the length of the other. There is no cytostome, 

 but a contractile vacuole is present. They produce minute spherical 

 cysts. 



Yakimoff and Solowzofl^ (1921r/) identified as Monas vulgaris a flagellate 

 they obtained by inoculation of agar plates with human faeces in Russia. 

 Yakimoff and his co-workers seem to believe that this affords sufficient 

 evidence of parasitism in the human intestine. The organism is un- 

 doubtedly a free-living form which in the encysted condition contami- 

 nated the stool after it had been passed. 



Genus: Heteromita Dujardin, 1841. 



This genus was established by Dujardin for certain flagellates which 

 had hitherto been included in the genera Monas or Bodo, and which pos- 

 sessed pear-shaped bodies provided with two anterior flagella, one of which 

 was two or three times as long as the other. The longer flagellum, which 

 was finer than the shorter one, could function as a trailing flagellum. It 

 seems not improbable that the flagellate for w^hich Krassilstschik (1886) 

 created the genus Cercobodo and that for which Klebs (1892) proposed 

 the name Dimorpha really belong to the genus Heteromita. Several 

 flagellates of this genus were studied by Dallinger and Drysdale, for one 

 of which Kent (1880-1882) proposed the name Heterotnita uncinata. 



The genus Heteroinita can be defined as including minute flagellates 

 which have pear-shaped bodies from the more pointed anterior end of 

 which arise two flagella of unequal length. The shorter one, which may be 

 thicker than the other, is from once to twice the length of the body and is 

 directed forwards. The finer and longer flagellum may be two to four 

 times the length of the body. It performs lashing movements, and when 

 in contact with a surface may act as a trailing flagellum. The axonemes of 

 the flagella, which commence in blepharoplasts on the nuclear membrane, 

 pass to the anterior end of the body, and thence directly into the flagella. 

 There is no cytostome, and a contractile vacuole is present in the posterior 

 region of the body. The body is exceedingly amoeboid when in contact 

 with a surface. In this condition the flagella may be lost, the flagellate 

 then moving about like a small amoeba. 



Reproduction is by longitudinal fission of free-swimming forms, or 



