424 ORDER FLAGELLATA-EUSTOMATA. 



prominent upper lip ; oral aperture distinct, opening on the anterior truncate 

 border, followed by a conspicuous pharyngeal tract ; flagella two in number, 

 subequal, both vibratile, the one spirally coiled and anchoring the animal- 

 cule to submerged objects when at rest ; contractile vesicle usually at the 

 anterior extremity ; endoplast conspicuous ; increasing by longitudinal 

 fission. Inhabiting salt and fresh water. 



By the earlier investigators it was left as a matter of considerable doubt whether 

 the members of this genus possessed a single flagellate organ only, or two of these 

 appendages ; Ehrenberg favouring the latter and Dujardin the former of these 

 alternatives. More recent investigation has established the accuracy of Ehrenberg's 

 anticipation. Diesing, premising that the animalcule described by these respective 

 authorities under the title of Chilomonas faratncedum included two distinct types, 

 has proposed to separate Dujardin's supposed monoflagellate variety under the title 

 of Plagiomastix, associating with it the doubtful Chilomonas obliqua of the same 

 writer and the Pleuromonas jaculans of Perty. Such a generic group, however, based 

 upon Dujardin's misinterpretation of the characters of the flagella, has no just claim 

 for recognition. Perty's Pleuromonas jaculans, on the other hand, is an entirely 

 distinct infusorial form. As now known, the representatives of the genus Chilomonas 

 correspond remarkably in general contour with those of Cryptomonas, previously 

 described, and are to be distinguished from them only by the absence of the lateral 

 pigment-bands which so conspicuously characterize that generic form, in common 

 with all the other members of the Chrysomonadidae. 



Chilomonas paramseeium, Ehr. PL. XXIV. FIGS. SI^ND 52. 



Body plastic, elongate-ovate, about two and a half times asS<^ig as 

 broad, widest anteriorly, tapering to a rounded point posteriorly, and 

 usually curved slightly towards the dorsal aspect ; cuticular surface smooth ; 

 endoplasm transparent, colourless, enclosing numerous large spheroidal cor- 

 puscles ; anterior border obliquely truncate, oral aperture situated in the 

 centre of this border ; the two flagella inserted at the apical extremity 

 immediately beneath the lip-like prominence, subequal in size, not so long 

 as the body ; pharyngeal tract narrow and elongate, continuous with the 

 central axis of the body through nearly half its length, finely striate longi- 

 tudinally ; contractile vesicle situated at a little distance from the margin 

 of the lip-like frontal prominence ; endoplast spherical, located at a 

 distance of one-third of the entire length of the body from the posterior 

 extremity. Length 1-1125" to 1-650". HAB. Vegetable infusions. 



O. Biitschli * regards this species as identical with both the Chilomonas gramilosa 

 and Zygoselmis nebulosa of Dujardin, and further proposes to unite with it the animal- 

 cule next described under the name of Chilomonas cylindrica. That the last-named form 

 is, however, essentially distinct is presently demonstrated, while Zygoselmis, as already 

 shown, belongs to a separate family group. The species now under consideration 

 occurs abundantly in vegetable infusions, and yields many points of interest. Treated 

 with acetic acid, Biitschli found that the animalcules threw out on every side ray- 

 like prolongations mingled with minute granular bodies whose nature would seem 

 most closely to approach the trichocysts of the higher Ciliata. He was however 

 unable to detect any trace of these structures in the living individuals. When isolated 

 on a glass slide for investigation the animalcules quickly lose their normal contour, 

 become more and more spherical, finally bursting and breaking up. Increase by 



* 'Zeitschrift fur Wissenschaftliche Zoologie,' Bd. xxx., Jan. 1878. 



