144 THE AMERICAN MONTHLY [ August, 
granular; contracted zooid obovate, often nodding, the pedicle invaginate 
within the posterior body region. Length ;4, inch. Hab.—Attached to 
Cypris and Cyclops in the pools of early spring. 
This form closely resembles /?habdostyla tnvaginata Stokes in contour, 
in the invagination of the pedicle by the contracted body, and in its habitat, 
but differing conspicuously in the much shorter pedicle, the more posterior 
position of the pulsating vesicle, and particularly in the form of the ciliary 
disc, this region in RZ. zxvaginata being markedly conical, while in 72. 
vernalzs it is usually evenly convex. The two species also differ widely in 
size. 
Reproduction of the present form takes place by longitudinal fission, and 
by encystment. The former method was observed by De Fromentil in an 
infusorian now regulated to the genus Rhabdostyla, but, so far as I know, 
has not been seen with any other species. Here, however, it takes place 
rapidly. The body widens until the breadth is nearly equal to the length, 
and then divides into two longitudinal parts, the moiety which will finally 
develop an independent pedicle remaining attached to the original foot-stalk 
by the tip of its posterior extremity until the production of a ciliary girdle, by 
means of which it becomes temporarily free-swimming. This ciliary ring 
is developed within a constriction formed around the body at about one-third 
its length from the posterior extremity, the free-swimming zooid being a 
short pyriform creature with rapid movements. Its free phase, however, is 
of limited duration, and its subsequent history is essentially that of the natatory 
zooid of Vorticella. 
When reproduction by encystment is about to be accomplished, the body 
surrounds itself by an ovate, apparently chitinous, cyst, which remains at- 
tached to the pedicle. The walls are thick, and the surface is minutely tuber- 
culate, the anterior extremity being centrally pierced bya circular orifice and 
surrounded by a short, neck-like projection (Fig. 8). The cyst is colorless 
when first formed, but soon becomes brown. The enclosed body gradually 
shrinks from the walls and becomes ovid, but the subsequeut processes 
are not known. Although I have obtained these infusoria in abundance, 
indeed, in the greatest profusion, and have repeatedly witnessed their assump- 
tion of the encysted phase, yet I have never observed subdivision, spore 
formation, nor any other reproductive method. The encysted animalcules, 
so far as my observations extend, remain quiescent and unchanged for an 
_ indefinite and unknown time. Attempts to preserve them in a life-cell have 
proved fruitless. Even in this condition of quiescence they appear to need 
the influence of moving water obtained by the active motions of the Cypris, 
Cyclops, or Canthocamptus bearing them. The infusorians were obtained 
from shallow pools as early in the year as the middle of February. 
Rhabdostyla cheticola, sp. nov. (Fig. 9.) 
Body elongate-ovate, somewhat changeable in shape, slightly gibbous, 
about four times as long as broad, widest centrally, constricted anteriorly 
beneath the peristome border, the posterior extremity narrowed to produce 
a subcylindrical prolongation about one-eighth the length of the entire body ; 
peristome everted, not revolute ; its width slightly exceeding that of the body ; 
ciliary disc scarcely exserted; cuticular surface finely striate transversely ; 
pedicle short, about one-eighth as long as the body, invaginate within the 
posterior extremity of the contracted body. Length of the zooid 345 inch. 
Hab.—Pond water; attached to the dorso-lateral sete: of /Vazs. 
Vorticella similis, sp. nov. (Fig. to.) 
Body broadly campanulate, only slightly longer than wide, very finely 
striate transversely, soft and somewhat changeable in shape, constricted be- 
neath the peristome border, thence widening and tapering in almost straight 
