HABITS OF YELLOW PERCH. 353 
TABLE 11.—RATE oF DIGESTION OF VARIOUS Foops AT A NEARLY UNIFORM TEMPERATURE, 16.6° C.4 
Time in hours until first feces. 
Temperature 
(degrees centigrade). Food eaten. 
Shortest.| Longest. | Average. 
16.50.58 5-0 7-0 6.0 
16.3... 4:5 6.8 5-4 
16.8. 7-16 23-0 19-2 
16.8. 5-5 24.0 8.4 
16.5. 3-25 23.0 b 135.8 
17-0.. 24-0 24-0 € 24.0 
@ xo perch were used; minimum weight, 1.9 g.; maximum weight, 4.67 g.; average weight, 2.85 g. When possible, as with 
chironomid larve and earthworms, the rate of digestion was computed from the time the fish began to eat; in a few cases 
(Entomostraca), from the time the food was placed in the dish. The experiments extended from Sept. 16 to Oct. 2, 1916. 
© Not eaten by 5 individuals. 
¢ Not eaten by 3 individuals. 
TABLE 12.—RATE OF DIGESTION OF VARIOUS Foops AT TEMPERATURES OF ABOUT 3 AND 18° C.¢ 
Temper- Food eaten. Average 
ature pe A EE ee eee ee ete 
Date. (dese digestion 
centigrade). Kind. Number-} (hours), 
Jan..24,1917...-... 2.5 3 43-7 
1 bcd Seaaioee 18.0 16 22.0 
Jan. 17,1917. 2-5 (?) 47-5 
JRiarssXOr7s. 0. 18.0 (@) 23.0 
Dec, 18, 1916....... 3-5 | Dikerogammarus.. 3 64-0 
AD f:\s Ot -Pp <-> > Pe 2.5 | Earthworms I 390 
10 yee SaaS 17-0 I 18.4 
Jan. 22.1917..... 2.5 ° 3 OY 
COREE CS 7 SEES 2.5 I 43-3 
20.5 I 16.4 
4:5 aaa 
_ 42 experiments were conducted simultaneously, using 2 perch in each case, averaging 28 g. in weight. When possible, as 
with chironomid larve and earthworms, the rate of digestion was computed from the time the fish began to eat; in a few cases 
(Corethra larvz), from the time the food was placed in the dish. 
TABLE 13.—RaTE oF DIGESTION OF VARIOUS Foops aT TEMPERATURES VARYING FROM 23 TO 26° C.4 
Food eaten. 
Yemipery! 22.6 3 ed Se es Aerie 
ature rate of 
Date. (degrees Number. Volume (c. ¢.). diges- 
centi- 2 tion 
grade), Kind. (hours). 
Total. | Perhour.| Total. | Per hour. 
{EOS ARCO, GMS: Ber raeeS Sate ree, 23 | Damselfly nymphs............ 24 1-5 2-5 0.15 31-7 
July 20, 1916.. = : 26 | Earthworms. ......+..-++6-005 5 2 2.0 +16 20.0 
July 5)1916.......+... 23) MIMD WS cit cue ome cea duatt oe 13 +57 5-2 -23 22.5 
@1n this experiment 1 perch weighing 48 g. was used. 
TABLE 14.—RATE oF DIGESTION oF VaRIOUS Foops AT TEMPERATURES VARYING FROM 2.5 TO 4.5° C.2 
Temper- Food eaten. Average 
Date. ature rate of 
(degrees : digestion 
centigrade). Kind, Number. | (hours). 
Jan, 24,1917 2 5s} osronomiid TArVesp sec dere ose cee ta se etna e 50 46-5 
Jan. 15,1917. . 2.5 | Corethra larv@............0.000s eh. (?) 48.0 
Dec. 18,1916. . 3-0 | Dikerogammarus aete 3 64.0 
Jan. 8, 1917... B.6 | ALCO WOkttS. «6 deine nae cos eile sina ona ° 
Jan. 22,1917. . 2.5 | Liver and flour. . Aree ° 
Jan. 1,1917... 2.5 | Minnows..... ey] 6 
Dec, 26,1916... 4-5 | Snails.... ° 
In this experiment a perch, weighing respectively 31 and 24 g., were used, 
