GENUS MONAS. 235 



tapering towards the opposite extremity, and there prolonged in an attenuate 

 tail-hke manner, the sarcode of this tail-like prolongation often ragged in 

 outline or irregularly branched ; flagellum flexible throughout, equalling the 

 body in length ; contractile vesicle posteriorly located ; endoplast con- 

 spicuous, spherical, subcentral. Length of elongate-ovate zooids 1-1500". 

 Hab. — Vegetable infusions. 



The species agreeing with the foregoing diagnosis, and, so far as it is possible to 

 determine, identical with the Monas fluida of Dujardin, has been obtained abundantly 

 by the author from hay infusions in fresh water. It usually makes its appearance on 

 the fourth day of maceration, and is often for the next day or two the most abundant 

 and dominant type, finally succumbing, however, in its turn to the onslaughts of its 

 more powerful congeners Di/iomonas vorax and tubercidatus hereafter described. 

 The varieties of contour assumed by this remarkably plastic monad are too numerous 

 for description ; but a few of the more prominent of these are illustrated in the 

 accompanying figures. In the most attenuate example the entire length of the 

 body, including the tail-like prolongation, is equal to seven or eight times its 

 greatest breadth. The characteristic plasticity of the sarcode of this type would 

 seem in all instances to attain its highest development at the posterior extremity ; 

 on many occasions individuals were observed to adhere by this region to the glass 

 object-carrier, and to become drawn out into an attenuate shape by the mere force 

 of the capillary currents induced by the partial evaporation of the water, lu this 

 method of adhesion the species may be said to advance a step towards the develop- 

 ment of a temporarily adhesive pedicle as obtains in the genus Oikomonas. Not 

 unfrequently the anterior extremity is abruptly or obliquely truncate, the animalcule 

 in the latter instance, when a subcylindrical contour is preserved, presenting an 

 appearance, excepting for the absence of the secondary flagellum, closely correspond- 

 ing with that of Chilomonas. The inception of particles of indigo at various points 

 of the periphery was frequently observed, as also the coalescence of two animalcules, 

 and the assumption by both these and by the solitary zooids of an encysted state. 

 The Monas sjiccissa of Perty, characterized by its ragged and not unfrequently 

 bifurcate posterior border, is possibly identical with this species. On altogether 

 insufiicient grounds Diesing has proposed to elevate this last-named type, as described 

 by Perty, into a new genus, conferring upon it the title of Dicercomotias. 



Monas ramulosa, Stein, sp. Pl. XIII. Figs, 22-24. 



Body elongate, subcylindrical, widest posteriorly, tapering and conical at 

 the anterior extremity, three or four times as long as broad, the entire 

 peripheral surface frequently produced into a greater or less number of 

 attenuate lobate or digitiform prolongations ; flagellum as long or longer 

 than the body ; contractile vesicle spherical, posteriorly located, sometimes 

 subdivided into three or four smaller vacuoles ; endoplast subcentral or 

 anteriorly situated ; endoplasm granulate. Length 1-650" to 1-325". 



Hab. — Fresh water. 



This animalcule is figured, but not described, in Stein's recent work ' Infusions- 

 thiere,' Abth, iii., 1878, under the name Cercomonas raimdosa ; but as in no one of 

 the examples deUneated is an indication given of the caudal filament which so essen- 

 tially characterizes the last-named genus as here amended, its transfer to the present 

 one has been decided on. In some respects the general contour and remarkable 

 modification of the cuticular surface approximate this type to the Monas fluida of 

 Dujardin ; but the prolongations of the surface of the periphery take a more definite 

 digitate appearance. Should this species, in common with many other members of 



