484 Birge—Vertical Distribution of Pelagic Crustacea. 
Fig. 2. Graphic representation of the percentile distribution 
of Diaptomus in the single observations of Period II. Each verti¬ 
cal line represents the total catch, 100 per cent., divided into 
10 per cent, intervals by horizontal lines. The lighter lines 
represent day observations, the heavier ones those taken at 
night. The first small circle with a dot within it marks the 
percentage found in the 0-3 m. level, the second circle adds that 
of the 3-6 m. level and the third that of the 6-9 m. level. The 
remainder of the line shows the percentage from the remaining 
9 m. The dotted horizontal line represents the average per 
cent, found in the 0-3 m. level and the line of dashes that of 
the 0-3 and 3-6 m. levels combined. The shorter lines indicate 
the average for day or night as they cross the light or heavy 
lines. It is plain that the upper levels are not so populous by 
night as by day, but the smaller absolute number found by 
night should also be noted. See p. 451. 
PLATE X. 
Fig. 1. Average percentile distribution of Diaptornus and day 
and night distribution by periods. The diagram is constructed 
in general like PI. IX, fig. 1. The night and day averages 
for each period are indicated and marked N or D. Those for 
each period are connected by a line numbered I, II, III, or IV. 
See p. 452, Table H. 
Fig. 2. Similar diagram for Cyclops; p. 462, Table K. 
Fig. 3. Similar diagram for D. hyalina; p. 467, Table N. 
The upper levels only are indicated in these diagrams as the 
numbers from deeper levels are too small to be platted. 
