126. Cercaria Inquieta.
C. mutabilis, convexa, cauda lævi. [Plate XXV.] Fig. 31 and 32. Changeable convex cercaria, with a smooth tail.
This animalculum so often changes the form of its body, that it is not easy to describe it; it is sometimes spherical, sometimes like a long cylinder, at other times of an oval figure, white and gelatinous; the tail is filiform and flexible, the upper part vibrating vehemently; no visible viscera; a pellucid globule may be observed at the base, and two very small black points placed near the top at d, Fig. 32; whether they be eyes to the animalculum is not known. It was found in salt water. a, Fig. 31, the body; b, the tail.
127. Cercaria Lemna.
C. mutabilis, subdepressa, cauda annulata. [Plate XXV.] Fig. 33, 34, and 35. Mutable cercaria, somewhat flattened, with an annulated tail.
This animalculum varies its form so much, that it might be mistaken for the proteus of Baker, though, in fact, it is totally different. The body sometimes appears of an oblong, sometimes of a triangular, and sometimes of a kidney shape. The tail is generally short, thick, and annulated, but sometimes long, flexible, cylindric, and without rings; vibrating, when stretched out, with so much velocity, that it appears as it were double. The intestines are not very distinct; a small pellucid globule, which Müller supposes to be its mouth, is observable at the apex; and two black points not easily discovered, he thinks are its eyes; sometimes it draws the tail entirely into the body. It walks slowly after taking three or four steps, and extends the tail, erecting it perpendicularly, shaking and bending it; in which state it very much resembles a leaf of the lemna. Fig. 33, a, the body rather spherical; b, the tail. Fig. 34, c, the triangular body; b, the tail. Fig. 35, the body extended; e e, the eyes; f f, the intestines; g, a large vesicle; h, a smaller one.
128. Cercaria Turbo.
C. globulosa, medio coarctata, cauda uniseta. [Plate XXV.] Fig. 30. Globular cercaria, the middle contracted, with a tail like a bristle.
Partly of an oval, and partly of a spherical shape, pellucid, and of a talky appearance. It seems to be composed of two globular bodies, the lowermost of which is the smallest; this figure is occasioned by the contraction at the middle. There are two black points, like eyes, even with a transverse line which crosses the upper part of this little creature; several large globules may also be discerned; the tail is sometimes quite straight, sometimes turned back on the body. It is to be found among duck-weed.