UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



ZOOLOGY 



Vol. 19, No. 7, pp. 275-281, 1 figure in text August 14, 1919 



r 



THE EXCRETORY SYSTEM OF A STYL 

 CERCARIA 1 



BY 



WILLIAM W". CORT 



In the summer of 1915 while working on the development of 

 trematodes at the University of Michigan Biological Station, Douglas 

 Lake, Michigan, I found Cercaria polyadena Cort in a small beach 

 pool on the north shore of the lake. This species of cercaria was 

 described from one specimen of Lymnaea reflexa Say from near Chi- 

 cago, Illinois (Cort, 1914, p. 16). At Douglas Lake I found it in 

 Lymnaea exilis Lea, Lymnaea emarginata angulata (Sowerby), 

 Lymnaea humilis nwdicella (Say), Lymnaea stagnalis appressa (Say), 

 and Lymnaea stagnalis perampla "Walker. "With an abundance of 

 material available it was possible to work out the details of the 

 excretory system of this cercaria by using the method described in a 

 previous publication (Cort, 1918). 



The excretory system of Cercaria polyadena is shown in figure 1. 

 The capillaries and flame cells of the postacetabular region were very 

 difficult to work out on account of the heavy cystogenous glands and 

 the crowding of the tubules in this region. Only two flame cells were 

 found in the posterior groups on each side, and the exact positions 

 of the flame cells of the next to the last groups were doubtful. The 

 excx-etory pore is located in the mid line within the cup-shaped depres- 

 sion into which the tail fits, and dorsad of that portion of the tail 

 within the depression. No part of the excretory system extends into 

 the tail. The muscular bladder (fig. 1, b) is Y-shaped or bicornuate, 

 with the horns about the same length as the main stem. The common 

 collecting tubes (cct) on each side which enter the tips of the horns 

 of the bladder are complexly coiled and receive the anterior and 

 posterior collecting tubes (act, pet) at the level of the acetabulum. 



i A research study from the University of Michigan Biological Station. 



