24 ZOOLOGY. 
sufficiently transparent to allow six or eight smaller bodies of the same — 
nature, but of a darker-green color, to be seen moving freely about the 
interior, which are the young; and even these, towards the period of their 
exclusion, contain another set of germs. The rupture of the exterior of the 
large body sets the small ones free. 
Bursaria vesiculosa (fig. 3) lives in the rectum of frogs; it is oval, and 
the margin is provided with vibrillee: size one twentieth ofa line. - 
Proteus diffluens (the genus has also been named Ameba) (jig. 2), - 
seldom exceeds one twenty-fourth of a line in size. It resembles a mass of. 
translucent jelly, which is continually changing its form from rounded to 
linear or cordate, sometimes projecting parts of the margin in various 
directions, so as to present a most varied outline. . 
Cyclidium glaucoma (fig. 8) is remarkable for its peculiar motion, which 
resembles that of the genus Gyrinus, a waterbug, which swims rapidly in 
circles on the surface of the water. ; 
Trichodina cometa (fig. 14) is one twenty-fourth of a line long, and lives 
as a parasite upon the fresh-water polyps (jig. 21), of which it gnaws the 
arms, causing death. 
Urocentrum turbo (fig. 18) has an oval-triangular, translucent body, and 
a stem about one third of its length. Length from one thirty-sixth to one 
twenty-fourth of a line. Found among duck-weed. 
Carchesium polypinum (fig. 20) has a bell-shaped body, mounted upon a 
slender, spiral, branched stem, formed by incomplete division. Found 
among aquatic plants. 
Enterodela (with the intestines evident). 
Opercularia articulata (pl. 75, fig. 17) is composed of a stout-branched 
stem, two or three lines long, each of which supports a bell-shaped body, 
which is subject to variations in shape. It attaches itself to water insects, 
and is sometimes so abundant upon them as to present the appearance of a 
covering of mould. 
Stentor mylleri (fig. 18) inhabits aquatic plants; when extended, it is 
shaped like a trumpet or funnel, but when contracted, it exhibits the form 
represented in the plate. Its length varies according to the amount of its 
contraction, from one tenth to one half a line. 
Cryptomonas ovata (fig. 4) is a lengthened green body, one forty-eighth of 
a line long, provided with a delicate shield. 
Bursaria truncatella (fig. 12) is somewhat egg-shaped, with one end 
deeply excavated: one fourth to one third of a line long. 
Chilodon cucullatus (fig. 10) is somewhat lengthened, flat, and rounded, 
with a small projection in front. Common in stagnant water. 
Trachelocerca olor (fig. 5) takes its trivial name from the distant 
resemblance it bears to a swan. It lives among duck-weed and conferva, © 
and is from one twenty-fourth to one twentieth of a line long. 
228 
