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THE EXCRETORY SYSTEM IN DIGENEA (TREMATODA). 
IV. A STUDY OF THE STRUCTURE AND DEVELOPMENT OF THE 
EXCRETORY SYSTEM IN A CYSTOCERCOUS LARVA, 
CERGARIA PEKINENSIS NOV. SPEC. 
By ERNEST CARROLL FAUST. 
(From the Department of Pathology, Peking Union Medical College, 
Peking, China.) 
(With 6 Text-figures.) 
The first record of a cystocercous cercaria was published by Wright (1885). 
Since that time Braun (1891), Ward (1916), Faust (1918) and Pratt (1919) 
have contributed to the general morphology of the group. But apart from the 
collecting reservoir or bladder at the posterior end of the body and the lateral 
collecting tubules immediately emptying into the bladder the excretory system 
of these larvae has not been studied. It is the purpose of this paper to lay 
especial emphasis on this system. 
Description of Cercaria pekinensis nov. spec. 
This larva was obtained from the testis of Vivipara lapillorum (Heude), 
taken from the Grand Canal, outside the East Wall, and from the North Lake, 
Imperial City, Peking. At first it was not easy to distinguish this species from 
the large non-bilharzian furcocercous larvae, but a careful study soon made 
the differences apparent. The movement is characteristically that of the cysto¬ 
cercous larvae, namely, backward instead of forward. The furci are distinctly 
flapper-like. The posterior portion of the body is partially enveloped by the 
distal portion of the tail. This tendency of the tail to surround the body is 
characteristic of the group. In Cercaria mirahilis, C. wrightii, C. anchoroides, 
and C. macrostoma the body is completely enclosed in the anterior portion of 
the tail, while in C. stephanocauda the enveloping tissue is only slightly de¬ 
veloped. In this as well as other particulars Cercaria pekinensis bears a striking 
resemblance to C. hrookoveri (Faust 1918). 
C. pekinensis has a body measurement of 0*7 to 0*74 mm. in length by 
0-21 to 0-26 mm. in transverse diameter. The tail trunk is 1-5 mm lon^ by 
0-21 mm. in diameter while the furci are 0-57 mm. long by 0-16 mm. in trans¬ 
verse measurement. Neither body nor tail has any mammillations or other 
permanent differentiations of the integument such as characterise most of 
