1914] Esterly: Schizopoda of the San Biego Eegion 139 



above 100 meters than is Euphausia. Both forms show a great increase 

 in numbers between 9 and 100 meters during the period from 2 a.m. 

 to 6 a.m. Nothing can be added here to what was said above concern- 

 ing the behavior of Euphausia as shown by the Kofoid net. Though 

 this distribution suggests that diurnal migration takes place, it can 

 not be shown more certainly, because we know nothing about the 

 occurrence of the animals at any depth from 6 p.m. to 2 a.m. 



Nyctiphanes appeared in four Nansen hauls out of 643 ; the suc- 

 cessful ones were in November and December, and they contained 

 eleven animals. These four hauls were all made above 137 meters and 

 between 4 and 6 a.m. These results agree, as far as they go, with 

 those of the Kofoid nets, but the puzzling question is, why were there 

 so few animals in the Nansen hauls when these are compared with 

 the other hauls ? There is evidence in table 11 that the animals were 

 present at depths above 200 meters in fairly large numbers, but that 

 would never be shown by the Nansen hauls alone. The answer to the 

 question can not be given at this time. In table 12 it was shown that 

 Nyctiphanes is more abundant on the surface between 4 and 6 a.m., 

 and in table 8 it appears that the optimum temperatures lie between 

 14 ?1 and 17°. It is desirable to inquire whether there is a relation 

 between the time of day and the surface temperatures in regard to 

 the abundance of the organisms. Table 14 contains the data for this. 



TABLE 14 



Surface Distribution op Nyctiphanes During the Winter, According to the Time 



OF Day But Within the Temperatures 14?1-17° 



A.M. 



















Time of 

 Day 



No. 

 Total 



of hauls : 

 Success. 



No. 

 Total 



of hours : 



Success. 



No. of 

 Total 



animals : 

 Per hour 



Frequency : 

 Haul Time 



1. 6- 8 



11 



4 



14 



4.1 



103 



7.4 



18 



30 



2. 8-10 



15 



4 



10.3 



3.2 



4 



0.4 



20 



32 



3. 10- 2 



















(16 hrs.) 



25 







21.9 























4. 2- 4 



1 







1.6 























5. 4- 6 



9 



6 



11.6 



6.7 



382 



33.0 



66 



58 



The table is self-explanatory, and gives reason for believing that, 

 even if hauls are made at temperatures between 14? 1 and 17°, they 

 will probably obtain small numbers of animals unless they come be- 

 tween 4 and 8 a.m., while the likelihood of large catches is increased 

 between 4 and 6 a.m. The table shows, furthermore, that the lack of 

 success during the sixteen hours from 10 a.m. to 2 a.m. is not due 



