142 THE AMERICAN MONTHLY ' [August, 
pond water. Movements extremely rapid and rotatory on the longitudinal 
axis, the anterior flagella then rigidly extended at right angles to the body, 
their distal extremities alone vibrating. 
The endoplasm seems to be semi-fluid ; it is remarkably soft, rapidly cir- 
culating within the flexible but firmer ectoplasm, carrying in its course the 
enclosed granules, and also apparently the contractile vesicle. In reference 
to the latter it is difficult to determine, as the infusorian’s quiescent periods 
are neither long nor frequent, but the contractile vesicle certainly seems to 
expand when near the posterior extremity, pass with the current to a certain 
point on the anterolateral border, and there to contract and disappear. 
Chloromonas pulcherrima, sp. nov. (Fig. 4). 
Body subfusiform, less than six times as long as broad, the posterior region 
narrowed and produced as a colorless, somewhat flexible, tail-like prolonga- 
tion forming about one-sixth of the entire length of the body, and sometimes 
slightly curved, its extremity truncate, often somewhat dilated, and usually 
bearing several short, fine sete ; the anterior border obtusely pointed, sur- 
rounded by three or four rows of divergent, acuminate, colorless spines, for- 
wardly directed ; the entire cuticular surface ornamented by rhombus-shaped 
depressions transversely placed, largest centrally, diminishing both anteriorly 
and posteriorly; lateral color bands distinct greenish-yellow, extending 
through the entire length of the body, except the tail-like prolongation ; 
flagellum shorter than the body; contractile vesicles two, situated on oppo- 
site sides of the lateral borders of the posterior body region; eye-spot not 
observed. Length of body 34, inch. Hab.—Shallow ponds in early spring., 
Movements somewhat irregular and vacillating, not rapid. 
Balanitizoon gyrans, sp. nov. (Fig. 5). 
Body ovate, about twice as long as broad, widest near the centre, thence 
tapering anteriorly, the borders rounded, the postero-lateral margins flattened, 
nearly straight, the body slightly narrowed at the truncate posterior extremity ; 
oval aperture central, projecting ; cilia clothing the anterior two-thirds of the 
body ; posterior seta single, sub-equal to the body in length ; pharyngeal pas- 
sage usually conspicuous ; contractile vesicle single placed at one end of the 
posterior extremity ; cuticular surface apparently transversely striate. Length 
of body joy to z#yq inch. Hab.—Standing pond water. Movements, by 
rapid revolutions on the longitudinal axis, with sudden lateral leaps. Re- 
production by both transverse and longitudinal fission. 
Gerda vernalts, sp. nov. (Fig. 6). 
Body soft, elongated, six to seven times as long as the widest part, the an- 
terior two-thirds subcylindrical, the posterior one-third somewhat inflated, 
about twice as wide as the anterior region, the posterior extremity abruptly 
tapering and obtusely pointed; peristome border revolute, ciliary disc 
obliquely elevated, ciliary circles two, the anterior wreath a spiral; cuticu- 
lar surface finely striate transversely ; nucleus long, narrow, hand-like, per- 
pendicularly placed near one lateral border; contractile vesicle spherical, 
situated in the inflated posterior region. Length when fully extended some- 
what less than ;4, inch. Habitat.—Shallow pools in early spring. 
Thus far I have observed but a single individual of this species, taking it 
on the first day of March from beneath ice a quarter of an inch thick. The 
little wayside pool was not more than three inches in depth, but it harbored 
very many infusoria, entomostrea, and rotifers. The cold water made 
my fingers painfully ache after a short immersion, yet these minute animals 
seemed as lively as in the warmth of summer. ' 
The body of G. vernalzs is rather longer in proportion to its width than 
is G. fixa of D’Udekem, but the two closely resemble each other in form. 
The differences however are conspicuous. The cuticular surface of G.fixa 
