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314 University of California Publications in Zoology (Vou.9 
13°8 to 20°5, and at salinities from 33.539 to 33.762. As in 
the case of other species, it is not possible here to separate the 
possible effects of temperature from the more evident effect 
of light. 
The hauls in which P. abdominalis was taken with the 
horizontal closing nets are summarized in table 40 which follows. 
It is scarcely necessary to point out the greater abundance be- 
tween 4 and 35 fathoms (line 1) at night, or the smaller num- 
bers taken at night as compared with the day catches between 
100 and 160 fathoms (line 3). 
TABLE 40 
Distribution of Pleuwromamma abdominalis as shown by hauls with the 
horizontal closing nets, day and night hauls compared 
A B Cc D E F 
Total Successful Total Total Animals per Haul 
Depth hauls hauls hours animals 10-hr. haul frequency 
Day Night Day Night Day Night Day Night Day Night Day Night 
4-35 29 27 0 3 8.8 7.8 0 45 0 57 (0) at 
50-75 12 8 1 1 3:3: 3:0 aL 1 3 3 8 12 
100-160 Sy ak 2 3 2.7 4.0 Wy IK) 60 25 25 27 
100-250 9 383 Ze 3.2 1.6 34.1 10 6 22 33 
300-550 7 O 0) Bed) 1020 0 3 0) 14 0 
The collections with the vertical closing nets (table 41) show 
that there is apparently an upward movement at night. The 
region of greatest abundance is below 200 fathoms (lines 4 and 
5) during the day, but this region is deserted at night. The 
animals were not taken above 100 fathoms except at night. 
TABLE 41 
Distribution of Pleuromamma abdominalis as shown by hauls with the 
vertical closing nets, day and night hauls compared 
f B C D 
Total Successful Total Animals per Haul 
Depth hauls hauls animals 100-f. haul frequency 
Day Night Day Night Day Night Day Night Day Night 
ie 40-0 106 100 0 4 0 4 Oo 0 4 
2. 100-40 39 34 0 4 0 5 0 8 0 11 
Os 200-100 12 7 7 4 27 7 27 7 58 57 
4. 250-200 6 1 6 0 29 0 58 0 100 0 
5. 300-250 4 1 3 0 28 0 56 0 75 0 
