3 1 8 ORDER FLAGELLA TA-PANTOSTOMA TA. 



Fam. XVI. HEXAMITID^J, S. K. 



Animalcules naked, free-swimming or temporarily adherent ; flagella 

 six in number ; no distinct oral aperture. 



GENUS I. HEXAMITA, Dujardin. 



Animalcules naked, free-swimming or temporarily adherent ; elongate- 

 ovate or subfusiform, but more or less plastic and variable in shape ; the 

 posterior extremity bearing two long, flexible, adhesive, caudal flagella ; four 

 long vibratile flagella produced from the anterior border ; endoplast and 

 contractile vesicle usually conspicuous ; no distinct oral aperture. Inhabit- 

 ing stagnant water and the intestinal viscera of Amphibia. Increasing by 

 longitudinal fission. 



Up to a comparatively recent date much doubt prevailed respecting the exist- 

 ence of the hexaflagellate animalcules, imperfectly described and connected with 

 the present generic title by Dujardin so long since as the year 1841.* Within the 

 last few years, however, various specific types have been rediscovered and subjected 

 to minute examination by Stein, Biitschli, and the present author, their place as 

 highly remarkable representatives of the Infusoria Flagellata being through such 

 investigation fully established. Among the data of note concerning the vital pheno- 

 mena of these singular animalcules, recorded for the first time in this volume, may 

 be mentioned their demonstrated capacity to lead a temporarily attached, in addition 

 to a natatory existence, as described in association with the two specific types 

 H. intestinalis and H. inflata. Although Stein has indicated in one of his drawings 

 the position of a presumed oral aperture, no trace of any such distinct inceptive area 

 has so far been detected by the author. Pending, consequently, the production 

 of more decisive evidence in this direction, it has been decided to relegate the 

 members of this generic group to the section of the Pantostomata. 



Hexamita intestinalis, Duj. PL. XIX. FIGS. 60-62. 



Body subfusiform, widest towards the anterior region, tapering and 

 pointed posteriorly, two or three times as long as broad, frequently with 

 one or two longitudinal dorsal sulci ; all six flagellate appendages similar 

 in size, equalling or exceeding the length of the body, the two posterior 

 trailing flagella inserted close to each other at the pointed posterior 

 extremity, the four anterior vibratile flagella originating in like manner 

 from the anterior or apical extremity ; contractile vesicle anteriorly located ; 

 endoplast spherical, subcentral. Length 1-2000" to 1-1500". 



HAB. Alimentary canal of Tritons and Batrachia. 



This species is illustrated by a large series of figures in Stein's recently pub- 

 lished volume, and has been obtained and examined in considerable abundance by 

 the author from frogs dissected at Professor Huxley's biological laboratory, South 

 Kensington, during the winter session of 1879 and 1880. In none of the illustrations 

 given by the first-named authority is, however, any indication given of the character- 

 istic habit manifested by the animalcules to attach themselves by their posterior 

 flagella, as observed by the author of both this and the species next described. When 



* F. Dujardin, 'Histoire des Zoophytes Infusoires,' Paris, 1841. 



