No. 390.] THE DISTRIBUTION OF MALLOMONAS. 489 
the temperature was practically constant from week to week, 
indicating a condition of stagnation. It was at the boundary 
line between the stagnant water and the slowly circulating 
TEMPERATURE 
a "O so’ 60° 70° 80° 
/0 
20 
tS 
My 
R 
S 30 
X DIAGRAM SHOWING THE 
N VERTICAL OISTAIBUTION OF 
ij MMALLONIONAS IN LAKE COCCHI TUATE 
a. £0 ON JULY 17,1896, ANO THE 
TEMPERATURE OF THE WATER 
AT VARIOUS DEPTHS ON THE 
SAME DATE. 
50 
60 
° 500 /000 1500 2000 
NUMEER OF MALLOMONAS PEA C.C. 
water above it that the Mallomonas reached their greatest 
growths. Below this depth the numbers decreased rapidly. 
A similar case of vertical distribution occurred in Whitehall 
Pond during the summer of 1897. This is a pond of dark 
