254 ORDER FLAGELLATA-PANTOSTOMATA. 



contractile vesicles two in number, subcentral ; endoplast posteriorly located. 

 Length 1-2000" to 1-1500". 



HAB. Hay infusions in both salt and fresh water. 



While agreeing considerably, both in general habits and external contour, as seen 

 under moderate amplification, with O. Steinii, last described, this species may be 

 readily distinguished from that type, on closer examination, by the recurved and 

 rostrate form of the anterior extremity, the rigid and arcuate flexure of the flagellum, 

 the presence of two contractile vesicles, and the frequent though not invariable de- 

 velopment of a more or less distinct pedicle. The type was obtained by the author 

 in equal abundance in hay infusions in both salt and fresh water, experimented with 

 in the months of January and February, at St. Heliers, Jersey, in the year 1879. 

 Examples in the latter medium appeared at the end of the first, while those in the 

 salt water were not observed until the end of the second week. When crowded 

 together in their attached state on the finer vegetable fibres and other debris, with 

 their bodies swaying to and fro and their anterior beak-like extremities and flagella 

 maintained in an active condition of elevation and depression, they present (as 

 shown at PI XIII. Fig. 73) a most grotesque resemblance to a group of little 

 birds bowing and chattering to one another. Figures 74 and 76 of the same plate 

 indicate the very considerable latitude of motion which the rostrum and accom- 

 panying flagellum possesses. The ingestion of solid food-particles at various points 

 of the periphery was observed on numerous occasions, as also the formation by 

 these animalcules of smooth spheroidal encystments. 



' 



Oikomonas quadratum, S. K. PL. XIII. FIG. 71. 



Body variable in shape, in its most typical sedentary condition, 

 irregularly quadrate or subpyriform, tapering and attenuate posteriorly, 

 attached to the chosen fulcrum of support by an attenuate thread-like 

 pedicle equal to or exceeding the length of the body ; flagellum very long, 

 curved or flexuose, twice or thrice the length of the body ; parenchyma 

 transparent, finely granular ; contractile vesicle single, situated towards the 

 anterior border ; endoplast subcentral. Length 1-1500". 



HAB. Pond water. 



This species was obtained in November 1871 on Anacharis in pond water 

 containing Codosiga botrytis, Anthophysa vegetans, and other ordinary fresh-water 

 Flagellata. It is readily distinguished from the preceding species by the great 

 attenuation of the posterior region and marked quadrate contour frequently exhibited 

 by the entire body. In the social group represented at PI. XIII. Fig. 71, the 

 example occupying the ' lowermost position to the extreme left, illustrates most 

 conspicuously this characteristic quadrate outline. In the two examples marked 

 a and b the ingestion of food-substances at opposite points of the periphery, as 

 observed by the author, is delineated. The contour adopted by the animalcule in 

 its free-swimming condition has not as yet been recorded. 



GENUS II. BODO, Ehrenberg. 



Animalcules ovate or elongate, free-swimming or temporarily attached, 

 exceedingly plastic and changeable in form, the anterior extremity having 

 a single vibratile flagellum, the posterior one prolonged into an attenuate 

 and persistent caudal filament ; no distinct oral aperture ; occurring mostly 

 as endoparasites within the intestinal viscera of various Vertebrates and 

 Invertebrates. 



