GENUS MEROTRICHA. 249 



Monadiform beings, coinciding in form with the representatives of the genus 

 Pleuromonas, as formulated by Max Perty, have been met by the author on several 

 occasions. Seeing, however, that similar forms represent the earlier or larval con- 

 ditions of other Flagellate organisms, such as Salpin^ceca fusiformis and Anthophysa 

 vegetans, the present retention of this genus must be regarded as entirely provisional. 

 It is, further, by no means improbable that the type P. jaculans, upon which the genus 

 has been founded, is identical with the Heteronema (Bodd) saltans of Ehrenberg, and 

 which, in addition to exhibiting similar leaping movements, appears under insufficient 

 magnifying power to possess a single flagellum only. 



Plenromonas jaculans, Pty. PL. XIII. FIGS. 43 AND 44. 



Body kidney-shaped, colourless, slightly granulate ; flagellum about three 

 times the length of the body. Movements eccentric, jerking and leaping. 

 Length 1-6000" to 1-3160". HAB. Stale water and infusions. 



The Pleuromonas granulosa of De Fromentel thus characterized : Body ovoid, 

 granular, rounded posteriorly, the anterior extremity attenuate, sharply recurved ; 

 flagellum proceeding from the apex of the anterior extremity, and often folded 

 between the recurved portion and the body ; parenchyma granulate ; contractile 

 vesicles two in number, posteriorly situated. Length 1-800" cannot be generally 

 associated with P. jaculans, and would seem to either represent the type of a new 

 genus, or possibly an imperfectly observed Heteromita. 



GENUS II. MEROTRICHA, Mereschkowski. 



Animalcules free-swimming, persistent in form, more or less ovate ; 

 flagellum single, issuing from a pit-like depression of the ventral surface ; 

 parenchyma enclosing trichocyst-like corpuscles. HAB. Fresh water. 



Merotricha bacillata, Mereschk. PL. XIII. FIG. 45. 



Body evenly ovate or elliptical, one and a half times as long as broad ; 

 ventral depression with associated flagellum situated at a short distance 

 from the anterior extremity ; a sheaf-shaped fascicle of rod-like trichocysts 

 occupying a median position at the anterior extremity; cuticular surface 

 entirely smooth ; endoplasm coloured green ; contractile vesicle situated 

 immediately behind the fascicle of trichocysts. Dimensions unrecorded. 



HAB. Fresh water : Lake Onega, Mereschkowski. 



This species, described by C. von Mereschkowski, in company with many newly 

 discovered Protozoic types,* is of special interest, it representing one of the very few 

 Flagellate animalcules in which the presence of trichocysts has been recorded. 



Fam. III. CERCOMONADID^S, S. K. 



Animalcules naked, free-swimming or adherent, provided with a per- 

 manent or temporarily developed caudal filament ; vibratile flagellum 

 single, terminal ; no distinct oral aperture. 



* " Studien iiber Protozoan des Nordlichen Russland," ' Archiv f. Mikrosk. Anatomic.' Bd. xvi., 

 1878. 



