124 



THE AMEEICAN MONTHLY 



[Jnly, 



new pharynx was produced, and the 

 hardy little infusorian extended its 

 shortened body and hurried oft" in the 

 same hasty way as if nothing unusual 

 had happened. 



In its contour it resembles T. pu- 

 sillum^ C. & L., differing chiefly in 

 the larger size, being from three to 

 four times greater, and in the more 

 spherical form of the nuclei. It is 

 shown extended in figure 3, magni- 

 fied 170 diameters. 



Litonohis pleu7'osigma^ sp. nov. 



Body linear-lanceolate, elongate, 

 flattened, somewhat sigmoid when 

 viewed ventrally, flexible and elastic, 

 length five or six times the breadth, 

 widest centrally, and tapering to each 

 extremity ; dorsal surface convex and 

 naked, the ventral flat, ciliated, lon- 

 gitudinally striated ; neck-like por- 

 tion equalling about one-fourth of 

 the length of the entire body, its 

 extremity curved toward the right ; 

 tail-like posterior extremity short, 

 obtusely pointed, somewhat curved 

 toward the left ; oral aperture sub- 

 terminal, very dilatable ; oral cilia 

 not conspicuously larger than the ven- 

 tral ; trichocysts few, long, scattered 

 throughout the body ; nuclei two, 

 ovate, subcentral, connected by a 

 funiculus ; contractile vesicles small, 

 numerous, the greater number ar- 

 ranged in a line along the left-hand 

 border, three or four dispersed along 

 the right-hand margin ; parenchyma 

 of the body coarsely, of the neck and 

 tail-like portions, finely granular ; 

 anal aperture postero- terminal. 

 Length of body ^4^ to ^\-^ inch. 

 Habitat. — The surface of dead leaves 

 and twigs at the bottom of shallow 

 pools. 



In form this animalcule resembles 

 Litonotus fasciola (Ehr.) S. K., 

 differing from it and from all other 

 species of the genus, in the multiple 

 contractile vesicles. It is somewhat 

 difficult to determine the exact num- 

 ber of these vacuoles. Usuall}^ twelve 

 can be counted, nine in a row along 

 the left-hand border and four on the 

 right, but as they come and go in ir- 



regular order the observer has quite 

 a task to count and omit none, the in- 

 fusorian being at the same time in 

 motion. 



The position of the oral aperture is 

 also characteristic. In the diagnosis 

 of the genus this orifice is stated to be 

 situated at the base of the neck-like 

 prolongation. With this species, 

 however, the writer has seen large 

 food masses enter through an opening 

 that is almost apical, and remarkably 

 elastic. On account of this sub-ter- 

 minal position it may hereafter be ad- 

 visable to relegate the infusorian to a 

 new^ genus. 



Conjugation of two individuals has 

 been repeatedly observed. Union 

 takes place between the anterior one- 

 half or two-thirds of the ventro-lateral 

 borders, but how long it continues I 

 have been unable to determine, as 

 none have become united during 

 my observations, all those noticed 

 having joined themselves previous to 

 capture, or being only on the point of 

 separating when first seen. Changes 

 in the neuclei were in each instance 

 sought for, but nothing unusual ap- 

 peared. 



Multiplication is by transverse fis- 

 sion, which, it is presumed, succeeds 

 conjugation. The posteriorly sep- 

 arating moiety possesses the caudal 

 prolongation of the mature zooid, the 

 freshly-divided surfaces being usually 

 evenly rounded. Within half an 

 hour, however, after complete sep- 

 aration, the neck-like portion is de- 

 veloped on the one, and the tail-like 

 prolongation on the other, so that 

 each infusorian then differs from the 

 mature animalcule in size chiefly, but, 

 at times, in the smaller perceptible 

 number of pulsating vacuoles. Im- 

 mediately after fission each part bears 

 a remarkable likeness to Litonotus 

 varsaviensis Wrz. 



In figure 4 is shown the lateral as- 

 pect, in figure 5 the ventral, and in 

 figure 6 two zooids in conjugation. 



Litonotus helus, sp. nov. (Greek, 

 helos^ a nail-head) . 



Body elongate-lanceolate, exten- 



