GENUS HERPETOMONAS. 245 



as observed were more repent than natatory, being chiefly confined to worm-like 

 writhings among the vegetable debris in which it was discovered. All the speci- 

 mens met with by the author possessed the perfectly transparent parenchyma 

 with the enclosed brilliant crimson corpuscules distinctive of the species. The 

 form figured and referred to this type by Cohn (reproduced by T. Jeffrey Bell, 

 'Quart. Jour. Mic. Sc.,' pi. xx., 1876) is altogether distinct, and an undoubted 

 Vibrio with a long flagelhim at each extremity. A far greater likeness exists, on 

 the other hand, between Ehrenberg's original drawings of Ophidomonas sanguined 

 and the " linear filaments of Bacterium rubescens" figured by Professor E. Ray 

 Lankester in a subsequent number of the same journal. 



GENUS VI. HERPETOMONAS, S. K. 

 (Greek, herpeton, snake ; monas.) 



Animalcules free-swimming, elongate or vermicular, highly flexible ; 

 the posterior extremity often the most attenuate, but not constituting a 

 distinct caudal appendage ; flagellum single, terminal ; contractile vesicle 

 usually conspicuous. Habits mostly endoparasitic. 



This new genus is instituted for the reception of the form figured by Stein, 

 ' Infusionsthiere,' Abth. iii., 1878, under the title of Cercomonas muscce-domesticce, 

 and identified by that authority with the Bodo musca-domestica of Burnett and the 

 Cercomonas muscarum of Leidy. The entire absence of a distinct caudal filament 

 serves, however, at once to distinguish it from the typical representatives of either 

 of the two last-named genera, and approximates it the more nearly to Leptomonas 

 or Ophidomonas. A second minute form recently discovered by Mr. T. R. Lewis in 

 the blood of rats is provisionally referred to this generic group. 



Herpetomonas muscse-domesticse, Burnett sp. PL. XIII. FIGS. 29-34. 



Body vermicular, highly flexible and polymorphic, usually thickest 

 centrally and tapering to a sharp point at each extremity, from ten to 

 twenty times as long as broad ; flagellum equalling or slightly exceeding 

 the body in length, thick at its base and becoming gradually more attenuate 

 towards the distal end ; parenchyma granular ; contractile vesicle single, 

 located near the anterior extremity; endoplast inconspicuous. Length 

 1-650" to 1-430". 



HAB. Intestine of common house-fly, Musca domestica. 



The synonyms of this species have been recorded in the preceding diagnosis of 

 the genus. According to the recent figures, with their descriptive indices given by 

 Stein, a more marked flexibility of the body, permitting the animalcule to assume 

 various snake-like and other contorted shapes, is especially characteristic of the 

 younger and smaller zooids. 



Herpetomonas Lewisi, S. K. PL. XIII. FIGS. 35-40. 



Animalcules exceedingly minute, attenuate and vermicular under 

 normal conditions, but highly polymorphic and capable of assuming a 

 variety of contours ; flagellum single, terminal, two or three times the length 

 of the extended body ; no contractile vesicle, endoplast, or other internal 

 differentiation as yet detected. Length 1-1500". 



HAB. The blood of Indian rats. 



