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 anotlier 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 vibrillas : size one twentieth of a line. 



Proteus dijluens (the genus has also been named Amoeba) {fig. 2), 

 seldom exceeds one twenty-fourth of a line in size. It resembles a mass of 

 translucent jelly, wljich 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. 



CycUdium 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 {fi^. 14) is one twenty-fourth of a line long, and lives 

 as a parasite upon the fresh-water polyps {fixf. 21), of which it gnaws the 

 arms, causing death. 



U^'ocentrum, turho {fig. 13) 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. 



CaTchesium 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 {pi. 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. 



Stenixxr 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 lengtli varies according to the amount of its 

 contraction, from one tenth to one half a line. 



Oryptomonas 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 cuGullatus {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 



