l^ll] Michael: Chactognatha of the San Diego Regiou. 101 



significance in relation to the conclusions of the "Kiel school" 

 is evident. 



The data in this paper contain numerous examples of this 

 lack of uniformity in distribution of the Chactognatha of the 

 San Diego region. Some of these examples are as follows : 



1. On July 18, 1908, two surface hauls, 1559 and 1560, were 

 made with the same net in the region of Cortez Banks at 32° 

 24:2 N and 119° 6:2 W. Haul 1559 was made at 6:20 a.m., 

 lasted 10 minutes, and contained 2,000 specimens of Sagitta 

 bipuncfata. Haul 1560 was made at 7 :20 a.m., lasted 40 min- 

 utes, and contained 527 of the same species. The temperature of 

 the water during each haul was 16?5 C. If, as indicated by the 

 temperature, the current remained uniform during both hauls, 

 then the net filtered four times more water during haul 1560 

 than during haul 1559. Consequently the number of 8. hipunc- 

 tata varied from 15 at 6 :20 a.m. to 1 at 7 :20 a.m. per unil 

 volume of water. 



2. On July 24, 1908, two surface hauls, 1597 and 1600, were 

 made with the same net. The temperature during each haul was 

 20?5 C, and the salinity varied from 33.549 during the first haul 

 to 33.603 during the second. Haul 1597 was made at 4 :26 a.m. 

 at 32° 51:4 N and 117° 22:2 W. Haul 1600 was made at 4:58 

 a.m., and the position of the " Agassiz" was 0:1 farther north and 

 0:4 farther west. Each haul lasted 20 minutes. Haul 1597 con- 

 tained 75 and haul 1600, 3 specimens of S. bipunctata. Thus the 

 number of specimens varied from 25 to 1 per unit volume of 

 water. 



3. On June 17, 1909, two surface hauls, 1659 and 1661, were 

 made with the same net while the ''Agassiz" was tied to its 

 mooring. Haul 1659 lasted from 5 :00 to 6 :00 p.m. and contained 

 13 specimens of S. bipuncfata. Haul 1661 lasted from 6:45 to 

 7 :30 p.m. and contained 550 specimens of the same species. 

 Unless the current changed between 5 :00 and 7 :30 p.m., the net 

 filtered one-fourth more water during haul 1659 than during 

 haul 1661 and the number of specimens obtained per unit volume 

 of water would be in the proportion of about 1 to 56. This differ- 

 ence is all the more striking when we consider that two other 

 hauls were made with the same net at the same mooring on the 



