SEASONAL CYCLE IN PERCH SPERMARY 683 
tribution of fish at different seasons. So far as the writer can 
determine, however, no thorough study has been made upon 
the seasonal changes that take place in the teleostean testis. 
It is the main purpose of this paper to describe the changes 
that have been observed in the testis of the yellow perch (Perca 
flavescens) during the different seasons of the year with refer- 
ence to the gross and microscopical anatomy and the cytology. 
II. MATERIAL AND METHOD 
The material for this investigation was collected from Lake 
Mendota at Madison, Wisconsin, and from Lake Michigan at 
Milwaukee, Wisconsin, between May 1, 1915, and October 1, 
1917. From five to twenty specimens were examined each week 
during this period. AIl were weighed fresh and the testes were 
weighed before fixation. Spermaries of other teleosts (carp, 
sunfish, crappie, pickerel, and lake trout), as well as those of 
Necturus, of two species of turtles, of several birds, and of the 
muskrat, were examined from time to time for comparison. 
For histological study material was fixed in 10 per cent formalin 
and in a picro-acetic acid mixture. Haematoxylin and haemalum 
stains were used with an eosin counterstain. Resorsin-fuchsin 
was used to stain the elastic tissue. 
In fixing material for cytological detail, Flemming’s, Gilson’s, 
and Bouin’s mixtures were used, the best results being obtained 
with Bouin’s mixture to which had been added a small propor- 
tion of urea (Allen, 716). Flemming’s triple stain, saffranin 
counterstained with licht griin and haematoxylin counterstained 
with eosin or licht griin were employed. Gentian violet alone 
also proved valuable. Sections from 5yu to 15u thick were used 
in the histological work. Both smears and sections were used 
in the cytological study, smears being prepared between cover- 
slips as described by Agar (711). 
The writer is indebted to Prof. A. S. Pearse for aid in collect- 
ing specimens in Madison, to Prof. M. F. Guyer for suggestions 
in technique and for criticisms, and to Prof. E. A. Birge, who 
kindly loaned a record which summarized the last fifteen years’ 
data on the temperature of the water of Lake Mendota. <Ac- 
