1912] Esterly: Copepoda of the San Diego Region 327 
Tiere im Freileben wichtige Wegweiser bei ihren Fluchtbewe- 
gungen, und deshalb dirigiren sie auch die Fluchtreflexe der 
Tiere im Laboratorium.’’ 
“Die Phototaxis ist bei den untersuchten Tieren also nur 
als ein kleiner Ausschnitt aus den Lebensgewohnheiten zu 
verstehen.”’ 
The author is justified in his claim that phototactic reactions 
are not in themselves vertical migrations. There can be hardly 
any doubt that the migrations take place, but it has been pointed 
out in the course of this paper, and elsewhere (e.g., Esterly, 
1911b), that a negative reaction to light does not seem to explain 
downward movements. Reactions to light are, as stated by 
Franz (1911a, p. 10), only a part (possibly not small) of the 
habits of the organisms, but it is difficult to avoid the conclusion 
that a reaction to light is the primary cause of the upward move- 
ment. The results in table 55 appear to show that the copepods 
follow a waning light in their upward migration. We may 
assume that the optimum intensity of light is low, judging from 
the depth at which the plurimum of most species is located 
during the day, and that the animals follow the optimum, so 
to speak. 
TABLE 55. 
Total numbers of animals and numbers per hour in ten species at surface during 
different periods of the night; totals at left, averages per hour at right 
in each column; bold face indicates plurima. When the average 
falls below 1, it is not entered. 
Number of specimens 
6-8 p.m. 8-10 p.m. 10-12 p.m. 12 p.m.-6 a.m, 
Calanus finmarchicus 3648 182.1 4285 973.7 3825 136 1842 44.7 
Bucalanus elongatus 403 920.1 321 73.2 0 1175 =. 28.2 
Euchirella pulchra 12 3 1 1 
Euchirella rostrata 9 2 0 5 
Labidocera trispinosa 2630 131.5 3 0 569 13.8 
Metridia lucens 1 228 52.0 31900 11390 6011 145.8 
Pleuromamma abdominalis 45 2.2 254 57.7 14 5 57 1.3 
Pleuromamma gracilis 1 165 37.5 15 5.4 32 
Rhincalanus nasutus 5 14 3.2 0 6 
Undeuchaeta bispinosa 1 21 4.8 2 1 
Totals 6750 5296 35757 9699 
Total hours of hauling 20 4.4 2.8 41.2 
Number of animals 
per hour haul 328.5 1203.6 12770 230.8 
