GENUS REPTOMONAS. 223 



immediately contracts into a subspheroidal contour, as shown in PI. I. Fig. 20. 

 It was observed that the granule circulation, conspicuously indicated in the central 

 substance of the body-sarcode, did not extend into the branched pseudopodic 

 extensions, neither on any occasion were these last-named appendages withdrawn 

 entirely within the periphery. 



Doubtful Species. 



The free-swimming flagellate amoebae, described by Tatem in the 'Monthly Micro- 

 scopical Journal' for June i86g, appeared at first sight to require a position in or 

 adjacent to the genus Masti^amoiha, but the result of a recent investigation into 

 the life-history of innumerable Pantostomatous Flagellate species, has inclined the 

 author to regard the forms there figured and described as merely metamorphosed 

 amoeboid phases of some such type as Monas fluida. 



Genus II. REPTOMONAS, S. K. 



(Latin, rcpto, to creep ; monas.) 



Animalcules repent, but slightly changeable in form, bearing a sino-lc 

 anterior flagellum ; locomotive pseudopodia produced only from the 

 repent or ventral surface. 



The limitation of the pseudopodia to the ventral region, and the conservation by 

 the body, taken as a whole, of a persistent contour, distinguish this genus from 

 Mastigamoeba, which it otherwise closely approaches. 



Reptomonas caudata, S. K. Pl. I. Figs. 31-33. 



Body monadiform, elongate-ovate, somewhat inflated posteriorly ; 

 flagellum slender, exceeding the body in length, produced from the apex 

 of the narrower and slightly pointed anterior extremity ; a long, trailing, 

 caudiform pseudopodium continued backwards from the posterior end of 

 the ventral surface, and numerous similar but smaller pseudopodia emitted 

 irregularly from the whole surface of this region ; contractile vesicle sino-Ie, 

 situated near anterior extremity ; endoplast spherical, subcentral. Leno-th, 

 exclusive of caudal pseudopodium, 1-1200" to 1-750". 



Hab. — Hay infusions, and among naturally decaying grass. 



This as yet single discovered species of the newly instituted genus Repto7)wnas 

 was obtained by the author in tolerable abundance from a hay infusion made at 

 St. Heliers, Jersey, in February 1879, a closely similar, if not absolutely identical, 

 specific type having also been met with among wet grass gathered in the Reo-ent's 

 Park in October of the same year, and under the circumstances narrated at length 

 at page 140. During progression the anterior extremity of the animalcule is usually 

 elevated in the manner shown at PI. I. Fig. 31, the flagellum meanwhile vibrating 

 vigorously in all directions in search of food. On one occasion, as delineated at 

 Fig- IZ, ^ Bacterium thrown by the vibrations of this organ against the anterior 

 margin was at once secured by an outflowing wave of the peripheral sarcode, and 

 rapidly passed into the interior of the body. l\\ many respects the animalcule' here 

 described presents a considerable resemblance to the Cercomonas crassicauda of 

 Dujardin, as reproduced from Stein's work at PI. XIV. Figs. 15 and 16. That type, 

 however, in common with all the representatives of the genus Cercomonas as here 

 accepted, is a free-swimming or natatory, and not a repent form. 



