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 Diaptomus 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. 



