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296 University of California Publications in Zoology | \Vou-9 
Inspection of table 22 will show that Eucalanus is both more 
abundant (lines 5 and 6) and more frequent (lines 7 and 8) 
by night than by day. In table 21 it is shown that the highest 
hourly average (column F) is obtained from about the middle 
to the end of evening twilight (line 8); the frequencies are 
also highest at that time (columns G and H). The curve of 
hourly averages at the surface for Eucalanus is in figure 2. 
8-10 10-12 12-2 2-4 4-6 6-8 8-10 10-12 12-2 2-4 4-6 
P.M. A.M. 
Fig. 2. Bucalanus elongatus. Variations in numbers per hour at the sur- 
face according to time of day. Data in table 21. 
The occurrence of Hucalanus is much more irregular at the 
surface than that of Calanus, as can be seen by comparing the 
curves of the two species (figs. 1 and 2). It is also noticeable 
that the former species was taken in a much smaller proportion 
of hauls than the latter (cf. lines 7 and 8 in table 22 with 
those in table 13). Notwithstanding this, both species occur 
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