128 University of Calif ovnia Puhlications in Zoology. [Vol.8 



While the above instances evidence considerable variation in 

 the rates of increase and decrease in abundance, as expressed 

 in the column of ratios, the data demonstrate that marked 

 decrease occurs about the time of sunrise and marked increase 

 directly after sunset. These facts strikingly confirm our former 

 inference that S. hipunctata migrates toward the surface during 

 subdued light and away during intense light and darkness. 

 To summarize, the facts and inferences respecting light are : 



1. During the night this species is most abundant between 

 the surface and 15 fathoms, while during the day it is most 

 abundant below 15 fathoms. 



2. The species appears in maximum abundance on the sur- 

 face and in 4-6 fathoms between 6 and 8 p.m., in 7-12 fathoms 

 between 4 and 6 a.m., in 15-20 fathoms between 8 and 10 a.m., 

 in 25-35 fathoms between noon and 2 p.m., and in 40-75 fathoms 

 between 10 a.m. and noon. 



3. In all depths above 20 fathoms the species attains two 

 maxima in abundance during the twenty-four hour day, one 

 occurring between 6 and 10 a.m.. and the other between 6 and 

 8 p.m. Below 20 fathoms only one maximum occurs and that 

 between 10 a.m. and 2 p.m. 



4. On the surface the species attains its morning maximum 

 within an hour after sunrise and its evening maximum within 

 an hour after sunset. 



5. It is probable that the species migrates toward that depth 

 in which twilight conditions are found. 



VARIATION IN DISTRIBUTION OF S. BIPUNCTATA DUE TO 

 TEMPERATURE 



A variation in surface temperature from 13 ?1 to 22? 3 C. is 

 noted in our data. During February it varied from 13 ?1 to 

 15?5, during ]\Iarch from 14?6 to 15?8, during April from 15?8 

 to 16?4, during June from 15?9 to 19?5, during July from 17?5 

 to 22?3, during August and September from 16?6 to 19?5, and 

 during November from 17?5 to 18?5. Hauls were not made nor 

 temperatures taken during January, May, October, and Decem- 

 ber. The variations noted, however, indicate that a minimum 



