1886.] 5uO [Stokes. 



usually trailing ; oral aperture conspicuous, communicating with a capa- 

 cious subtriangular pharyngeal cavity ; contractile vesicle single, spheri- 

 cal, near the anterior extremity ; nucleus subspherical, situated near the 

 body centre ; endoplasm enclosing numerous small ovate chlorophyl 

 corpuscles forming a bright-green layer near the cuticular surface. 

 Length of body ¥ |q inch. Movements rotary on the longitudinal axis, 

 but not rapid. Reproduction by encystment and subsequent binary 

 fission. Habitat — Pond-water. 



This is very similar to Raphidomonas semen (Ehr.) Stein, with two 

 flagella and no apparent trichocysts. When first observed, more than a 

 year ago, it was without hesitation identified with the above-mentioned 

 European form ; but some evenings later, while again examining the 

 Infusorians, it became evident that the specimens possessed two flagella, 

 while the Raphidomonas has but one ; otherwise they were identical with 

 the form just named, with the exception of the trichocysts. Recently the 

 same Infusoria have been collected in a locality remote from the first, 

 and the previous observations confirmed. 



The trailing flagellum is ordinarily extremely difficult to see. When 

 the Infusorium is rendered uncomfortable and sluggish by prolonged con- 

 finement beneath the cover-glass, or partially poisoned by iodine, then the 

 vibratile flagellum, which is usually held stiffly in advance, the tip alone 

 trembling, is flashed into sight as a rapidly undulating spiral, and the 

 trailing appendage is also momentarily directed forward. At other times 

 it also becomes visible when the Infusorian is in certain positions or has 

 assumed certain changes of form. How the careful European investigators 

 could have overlooked this trailing appendage is inexplicable, providing, of 

 course, that the present form is Raphidomonas semen, with which two 

 flagella are now for the first time observed. It is scarcely possible to be- 

 lieve that Stein would have failed to notice so important an appendage. 

 Yet these two forms are so nearly identical, with the exception of the bi- 

 flagellate character of the present Infusorian, that I confer the generic 

 title Trentonia provisionally only. If, after re-examination, the European 

 Raphidomonas should prove to be monoflagellate, then will Trentonia 

 flagellata become the type of a new family group necessarily taking the 

 name Trentonidse. 



Oryptoglena truncata, sp. nov. (Fig. 7). 



Lorica subspherical, depressed posteriorly, the anterior border rounded, 

 the oral aperture slightly eccentric and somewhat conically projecting ; the 

 posterior margin truncate, often slightly retuse ; the lower or ventral 

 aspect gently concave, the dorsal convex ; enclosed zooid subspherical ; 

 endoplasm green ; contractile vesicle double, anteriorly situated ; amyla- 

 ceous corpuscle single, subspherical and subcentrally located ; lorica 

 minutely punctate, colorless when young. Length r ^ 7 inch or less. 

 Habitat — Pond water. Movements rotary on the long axis. 



The enclosed body varies much in size. It is usually small, occupying 



PROC. AJ1ER. PHILOS. SOC. XXIII. 124. 3t. PRINTED DEC. 23, 1886. 



