TRICHOMONAS VAGINALIS 43 



It must also be pointed out that unicellular organisms with one or 

 several flagella are not always classified with Flagellates, for such forms 

 occur in Rhizopods as well as transiently in the lower plants. In addition 

 the examination of the Flagellates, especially the parasitic species, is very 

 difficult on account of their diminutive size and great activity ; thus it happens 

 that certain forms cannot with certainty be included in the group because 

 their description is insufficient. 



LITERATURE. 



BUTSCHLI, O. Protozoa in Bronn's Cl. u. Ord. d. Thierr, 1880-87. 



KLEBS, G. Organisation einig. Flagellatengrupp. (Unters. a. d. bot. Inst. Tubing, 

 1883, i-> 2 I z - f- wiss- Zool., 1892, Iv. 



BLOCHMANN, F. Mikrosk. Thierw. des Susswassers. 2nd edition, 1895. 

 KENT, S. Manual of the Infusoria. London, 1 880-81, i. 



A. Polymastigina, Blochm. 



The Flagellata parasitic in man, and best known, belong 

 to the Polymastigines, and to two genera that are easily dis- 

 tinguishable. 



Gen. i. Trichomonas, Donne, 1837. 



The body is generally pyriform, the anterior part usually rounded, the 

 posterior part pointed ; there are at the anterior extremity three or four equally 

 long flagella that are sometimes fused together ; in addition there is an 

 undulating membrane that commences at the anterior extremity and proceeds 

 obliquely backwards. The nucleus is situated at the anterior extremity, 

 and behind it are one or more vacuoles, none of which seem to be contrac- 

 tile. These flagellates are parasitic in vertebrate and invertebrate animals, 

 and live chiefly in the intestine. 



I. Trichomonas vaginalis, Donne. 



Form of body very variable, elongated, fusiform or pear-shaped, 

 also amoeboid ; the length varying between 0*015 an d 0*025 

 mm., and the breadth between 0*007 and 0*012. The posterior 

 extremity is drawn out to a point and is about half the length 

 of the remainder of the body. Cuticle very thin ; the body sub- 

 stance finely granular. At the anterior extremity there are three 

 some say four ] -^flagella of equal length which are frequently 

 united together, at least at the base, and easily fall off. 



There is an undulating membrane which runs spirally across 

 the body, arising from the place of insertion of the flagella, and 

 terminating at the base of the caudal process. Cytostom seldom 



1 To explain this discrepancy it is stated that the border of the undulating mem- 

 brane can raise itself off in the form of an independent flagellum. 



