C. membranacea, antice crassiuscula, truncata, cauda triplo breviore. Membranaceous, the fore-part rather thick, truncated, the tail three times shorter.
It is an oval, pellucid membrane, something larger than the monas lens. The fore-edge is thick and truncated, the hinder-part acute, and terminating in a short tail. It whirls about in various directions with great velocity.
143. Cercaria Discus.
C. orbicularis, cauda curvata. A small orbicular animalculum, with a bent tail.
144. Cercaria Orbis.
C. orbicularis, seta caudali duplici longissima. Orbicular cercaria, with a tail consisting of two very long bristles.
145. Cercaria Luna.
C. orbicularis, cauda lineari duplici brevi. This is likewise orbicular, with two short spines for a tail; the fore-part hollowed, so as to form a kind of crescent.
XII. LEUCOPHRA.
Vermis inconspicuus, pellucidus, undique ciliatus. An invisible worm, pellucid, and everywhere ciliated.