THE EXCRETORY SYSTEM IN DIGENEA. I. 



ERNEST CARROLL FAUST. 



NOTES ON THE EXCRETORY SYSTEM OF AN AMPHISTOME, 

 Cercaria convoluta, NOV. SPEC. 1 



Recently the excretory system of certain distomes has been 

 described. Sewall Wright (1912: 167-170) made a thorough 

 study of the system in the adult Micro phallus opacus. Cort 

 (1918, igiSa) and the writer (1918, 19183) have added to the 

 knowledge of these organs in cercariae and distomula. However, 

 no significant work on the excretory organs of amphistomes has 

 been published since the important monograph of Looss (1892) 

 on Diplodiscus subclavatus (Rudolphi). During the past year 

 the writer has been enabled to make a detailed study of the 

 cercaria and parthenita of an undescribed amphistome for which 

 the name Cercaria convoluta is proposed. Although the main 

 purpose of this paper is to elucidate the excretory system of this 

 amphistomulum, a brief description of the other organs is made 

 as a matter of record. 



Cercaria convoluta nov. spec. 



Host : Planorbis trivolvis Say. 

 Parthenita: redia. 

 Habitat: Urbana, Illinois. 

 Date: April to November, 1918. 

 Systematic position: Diplodiscinae. 



Cercaria convoluta is a pyriform larva, measuring from 0.4 

 to 0.76 mm. in length by 0.3 to 0.56 mm. in width. The tail is 

 approximately twice as long as the body. The oral cavity has a 

 maximum outer diameter of o.i mm. The acetabulum, situated 

 at the posterior margin of the body, has a width diameter of 

 0.16 mm. and a length diameter of 0.12 mm. It is directed 

 ventrad. The pharyngeal pockets are large and conspicuous. 



1 Contributions from the Zoological Laboratory of the University of Illinois, 

 No. 130. 



315 



