SEASONAL CYCLE IN PERCH SPERMARY 687 
They are fused together for a short distance at the point of the 
fusion of the testes, but they redivide, one cord passing into the 
connective-tissue core of each testis and, subdividing within, 
send one branch anteriorly and one posteriorly. Small branches 
extend into each of the connective-tissue septa in the form of 
JUNE JULY AUG. SEPT. OCT NOV. DEC. JAN. FEB. MAR APR MAY 
Fig. 1. A. Graphical illustration of volumetric variation in testis. Each 
space on the ordinate represents a period of one month. Each space on the 
abscissa represents a variation of 1 per cent in the ration between the body 
weight and the weight of the testis. B. Graphic representation of the seasonal 
variation in temperature in the water of Lake Mendota at a depth of 6 meters. 
Each vertical space represents a variation of 5°. Each horizontal space repre- 
sents a period of one month. 
