Mavor & Feinherg—LympJiocystis Vitrei 
559 
LYMPHOCYSTIS VITREL 
A NEW SPOROZOAN PROM THE PIKE-PERCH, 
STIZOSTEDION VITREUM, Mitchell 
' BY 
J. W. Mayor, S, M. Feinberg. 
In the course of investigations on the protozoan parasites of 
Wisconsin fishes a diseased condition of the skin and underlying 
tissue of the Wall-eyed Pike or Pike perch, {Stizostedion viU 
reum, Mitchell) came to our notice. The diseased fish were 
caught by the State Fish Commission at Minocqua, Wisconsin, on 
Ap;fil 29th and May 5th, 1915, and sent on ice to Madison for 
investigation. They were kindly turned over to us by Dean 
Birge and Professor Wagner of the University of Wisconsin. 
The diseased condition was, we understand, prevalent at that 
time in the Northern part of the state. Owing to the delay in¬ 
volved in the transport and turning over of the fish to us, the 
fish showed early stages of decay when they came into our hands, 
a fact which led to the somewhat imperfect preservation of our 
material. 
The observations on the fresh material were made by the 
senior author at a time when the press of teaching work neces¬ 
sitated their being rather brief. The external evidences of the 
disease, as seen in the dead fish, were numerous swellings on the 
surface of the body and on the fins (Plate IV, Pig. 1). The sur¬ 
faces of the swellings showed small round light colored eleva¬ 
tions which on dissection were found to contain white spherical 
bodies from .5 to 1 mm. in diameter. 
A microscopic examination of these cysts in the fresh state 
showed them to consist of a resistant transparent envelope filled 
with a granular mass surrounding a clear well defined central 
