. Fresh-water biology. Freshwater biology. PARASITIC FLATWORMS 4^5 193 (233) Tail slender, never as broad as body of cercaria. Cercariae leptocercae . 194 The long, slender, unbranched tail, which even in maximum contraction does not reach the width of the body, and in extension is twice the body length or more, is found in the majority of distome cercariae. The anterior end of the body furnishes data for the subdivision of these forms. 194 (199) Anterior end rounded, entirely devoid of spines. Gymnocephalous cercariae 195 So far as known these forms develop in rediae. Many exist on this conti
. Fresh-water biology. Freshwater biology. PARASITIC FLATWORMS 4^5 193 (233) Tail slender, never as broad as body of cercaria. Cercariae leptocercae . 194 The long, slender, unbranched tail, which even in maximum contraction does not reach the width of the body, and in extension is twice the body length or more, is found in the majority of distome cercariae. The anterior end of the body furnishes data for the subdivision of these forms. 194 (199) Anterior end rounded, entirely devoid of spines. Gymnocephalous cercariae 195 So far as known these forms develop in rediae. Many exist on this continent which have not been reported, for many adults are listed in the earlier sections of this key which must possess such larvae as one may infer from European studies on related species. These ceicariae are conveniently subdivided on the structure of the tail which in all is a prominent organ but which in some does not function as a swimming organ. 19s (196) Tail simple, not provided with fin-folds or terminal sucking organ. Three different forms may be noted without attempting to analyze them in the key. Cercaria (Gymnocephala) ascoidea (Leidy) 1877. Length to 0,4 mm. Body, white clavate; tail long, narrow, cylindrical, pointed. Cephalic end triangular and slightly constricted from rest of body. Acetabulum at or behind center of body often protruded into a cone or expanded into a cup. No eyes. In movement excessively elongated. Rediae white; head distinct from cylindrical body, with birth pore and caudal prolongation. Abundant in Planorhis parvus and found free in water containing that species. Leidy is in error in identifying this form as Cercaria minuta Nitzsch of Europe. Cercaria agilis Leidy 1858. Body pyriform, oral sucker large, acetabulum slightly larger, near middle of body. Tail as long as body, clavate, transversely phcate. White. Very active. Found in Delaware River; ordinarily with snails. Conmion. Cercaria fasciolae hepaticae. Larva of the well-known sheep l
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
