342 KOFOm AND SWEZY. 



stance as shown by the continuity of the cytoplasm about it, at least 

 upon the upper surface of the preparation, and by the presence of a 

 sHght fluid film of the food vacuole about it. We have also observed 

 a living trophozoite actually envelope one of these cysts having a vol- 

 ume nearly equal to its own, by an amoeboid engulfing movement 

 beginning at the cytostome. 



Cysts of this type were originally described by Perroncito (1S88) 

 and were regarded by him as belonging to Cercomonas (= Tricho- 

 monas) intestinalis. Schaudinn (1903) described their formation by 

 copulating and maturating Trichomonas intestinalis from man, and 

 Prowazek (1904) also related them to this species from the rat. Later 

 Bohne and Prowazek (1908) described autogamy in them and Bensen 



(1909) confirmed their results. Prowazek (1912) later again refers 

 these cysts to Trichomonas, but Wenyon (1910) associated them with 

 these flagellates only " as abnormal and degenerate forms." However, 

 Doflein (1911) in the latest edition of his "Lehrbuch" accepts the 

 cysts as those of Trichomonas but questions autogamy and reduction, 

 and Donitz and Hartmann have included them in their wall chart 

 of Trichomonas. 



Dobell (1908b) was the first to expressly doubt their relation to 

 flagellates and refer them to the yeasts or related organisms, a view 

 supported by the fuller investigation made by AlexeieiT (1911a, 1911c) 

 who determined their life-history and named the organism Blastocystis 

 eyiterocola. 



The activities of Tetratrichomonas prowazeJci resemble those of 

 Trichomonas augusta with which it is associated and in the living condi- 

 tion the two are readily confused. In stained material the additional 

 anterior flagellum, axostyle, contents of vacuoles, and absence of 

 axostylar chromidia at once differentiate it from Trichomonas. 



The extranuclear motor apparatus is identical in its component 

 organelles with that in Trichomonas except for the presence of four 

 instead of three anterior flagella. Alexeieff states that these are of 

 unequal length, there being two subequal long ones and two subequal 

 shorter ones. Our observations, Alexeieff's (1910), and Parisi's 



(1910) figures agree in indicating some variability in length, but we 

 find no constant morphological differentiation in these organelles. 



The undulating membrane is less developed than in Trichomonas 

 having less elevation, fewer undulations and a more slender and 

 usually relatively shorter chromatic basal rod. The axostyle is very 

 slender, exceedingly hyaline, devoid of chromidia, and without anterior 

 capitulum. It usually projects posteriorly (Fig. 68) as a slender 



