1912] Esterly: Copepoda of the San Diego Region 301 
TABLE 27 
Summary of table 26 
Day Night 
1. Total number of hauls 171 92, 
2. Number of successful hauls 1 24 
3. Total number of hours 85.8 68.3 
4. Number of suecessful hours 3.5 24.1 
5. Total number of animals 50. 38140 
6. Average per hour 0.6 573 
7. Haul frequency 6 25 
8. Time frequency 6 33 
Table 26, columns E and F, lines 9 and 10, shows that 
Metridia is overwhelmingly more abundant and frequent on 
the surface between 10 p.m. and 2 a.m.; a noticeable increase 
is observable from 8 to 10 p.m. (line 9). The time of great 
abundance for this species at the surface corresponds with that 
for Calanus and Eucalanus. Beginning with line 7 in table 26 
‘and following columns E, F, G and H through to line 12, it is 
noticeable that the numbers of animals and the frequencies 
inerease to the amounts in line 9; after that the numbers de- 
crease gradually to line 12, and the frequencies also, following 
line 10. The organisms are practically absent from the surface 
between 8 a.m. and 8 p.m. (lines 3-7). While this evidence 
of a diurnal migration is based on a comparatively small num- 
ber of hauls, it is so clear that we can hardly doubt its reliability. 
Figure 3 shows the varying numbers per hour at the surface 
in a curve which is made up from the data in table 26. 
