The holostome metacercariae were found in the fresh water fishes of Hyascdeotris swinbonis, macropodus opercularis, pseudorasbora parva and rasborcs saercthus in Guangdong area. These encysted metacercariae have been experimentally fed to ducklin.gs from which adult worms are obtained in the intestine. Two species have been identified, one is.Batemor ccidms described by Yamaguti, 1933 and the other is a new species and the name G'yathocot aense is given. The former requires B days to develop to adult after infeotion while the latter requires 4 days. Histological and histochemical structure of the cyst wall was studied. Eody pyriform, not concave ventrally, 0. T40-0. 996 -805mm. Of al suoker terminal, Anetabulum absent. Pharynx developed, Esophagus not distinct. Caeca extending to posterior extremity of body. Testes diagonal and varying in sire, Genital pore opening to the posterior terminal. of the body. dvary oval anl. anterior to the IePt. testis, Uterus very short, Vitellaria follicles numerous and well developed. Eggs large, 0.096--0.120 by 4.056-O.Ofimm, Definitive host: MaeroPodus oerrzc- dares, Pseacdorasborcc prva, Rrcsbor.us hneatlaus. sacion testine. Locality:Guang zhou, Guangdoxig Pravixice, China..pe specimen: Deposited in the Department of Parasitology Zhongsieal College, Guangahou C. s2raersse sp. nov. is morphologically similar to C. oraaL2s, but they differ from the proporation of the oral sucker and pharynx, position, and sire of the testis, distribution and number of vitelline follicles and the eggs in number. The outer wall of two species belong to areolar connective tisus, as well as theirrhemicr,I compositions, except cantaiuing a Little amount of theglycogen and Lipid, are consisted mainly of carbohydrate-protein complexes including tyrosine, muroprotein, neutral mucopalysaccharide and glycoproteixz. Vhile the inner wall of tava species is。 non cellular structure and belongs to collagenous fibers, its nature o# histoehemistry is sim ilar to that of outer wall except that it lacks oflid rind has less in c.mount of tho remaining elements. As for the origin o# the cyst wall, the outer waIl, similarly to that of the surrounding host tissue, is assumed to he origitzated from the host tissue and the inner wall may be formed from the excretory substances of tha parasite itself.