1887.] 247 [Stokes. 



SapropMlus {aa-po<pdoq), gen. nov. 



Animalcules free-swimming, holotrichous, ovate, soft, flexible and 

 changeable in shape : general cuticular surface clothed with fine vibratlle 

 cilia, a single, long, flexible seta projecting from the posterior extremity ; 

 oral aperture ventral, supplemented by a vibratile and retractile hood- 

 like membrane. 



SapropJiilus agitntus, sp. nov. Fig. 8. 



Body ovate, compressed, about twice as long as broad, the posterior 

 extremity rounded, the antero-ventral border obliquely truncate ; cuticu- 

 lar surface longitudinally striate, the cilia short and fine ; oral aperture 

 ovate, ventral, at a short distance from the anterior extremity ; the hood- 

 like membrane narrow, widest posteriorly, narrowing to its anterior ter- 

 mination ; contractile vesicle single, in the posterior body-half; nucleus 

 subspherical, subcentrally placed. Length of body, yi^y to -^^^ inch. 

 Hab. — An infusion containing much decaying animal matter. Reproduc- 

 tion by transverse fission. 



The hood-like velum resembles in character and function the oral 

 appendage of Pieuronema, widelj'- difi"ering, however, in its vibratile move- 

 ments, Pleuronema having only the power to lower and raise the organ, 

 while the present form possesses the additional ability to rapidly vibrate 

 the appendage. When retracted the latter is, similarly with the hood in 

 Pleuronema, folded and stowed away about the posterior and lateral mar- 

 gins of the mouth. 



The body is extremely soft, and quite changeable in shape, the latter, 

 however, usually consisting chiefly in the assumption of a subspherical 

 form. It has the power to force itself through small orifices, the body- 

 sarcode flowing almost as freely as a semi-fluid substance. 



These animalcules are essentially scavengers, greedily appropriating 

 decaying animal fragments, swarming in crowds around and within the 

 dead bodies of various small aquatic animals. Within the body of a dead 

 Gammarus they were crowded in profusion, there rapidly undergoing re- 

 productive fission, the process being probably hastened by the abundance 

 of stimulating food. 



Bothrostoma (iSoO/xx; ; (jzo/ia), gen. nov. 



Animalcules free-swimming, heterotrichous, ovate, soft and flexible ; 

 peristorae-field a more or less obliquely directed longitudinal depression, 

 situated on the left-hand side of the body, extending beyond the body- 

 centre, and continued inward as a short, ciliated, pharyngeal passage ; 

 the left-hand border of the peristome bearing a series of large cilia, the 

 posterior portion of the right-hand margin supporting an undulating mem- 

 brane; a cluster of long setose cilia projecting from the posterior ex- 

 tremity ; contractile vesicle and nucleus conspicuous ; anal aperture pos- 

 tero-terminal. Inhabiting fresh water. 



