122 University of California Puhlications in Zoology. [Vol. S 



in 15-20 fathoms from 27 to 908. Does this signify that the 

 intensity of light above 15 fathoms caused the species to migrate 

 downward, while that below 20 fathoms M^as subdued enough 

 to cause them to migrate upward? The data are too incom- 

 plete to warrant such a conclusion, but it is suggested from the 

 fact that the species attained its maximum abundance in 15-20 

 fathoms at this time. 



4. During the next period, 10 a.m. to noon, the number of 

 specimens on the surface decreased from 169 to 10 per hour, and 

 that in 15-20 fathoms decreased from 908 to 180, while the 

 species makes its first appearance in 40-75 fathoms, an average 

 of 177 specimens per hour having been obtained. Owing to lack 

 of collecting in 4-6, 7-12, and 25-35 fathoms at this time, the 

 meaning of this is uncertain. However, it is probable that the 

 intensity of light in 15-20 fathoms is much greater between 10 

 a.m. and noon than between 8 and 10 a.m., and if so we should 

 expect downward migrations from this depth. Similarly between 

 noon and 2 p.m. the maximum number of specimens was found 

 in 25-35 fathoms and the next most abundant number in 40-75 

 fathoms. 



5. From between 2 and 4, 4 and 6, and 6 and 8 p.m., the 

 number of specimens per hour on the surface increased from 

 19 to 153 to 889. In 7-12 fathoms it increased from 3 between 

 4 and 6 p.m. to 23 between 6 and 8 p.m. In 15-20 fathoms it 

 increased from 32 to 75 to 102. We should expect this evening 

 increase to begin first in deeper water and appear last on the 

 surface. Lack of hauling prevents determining this point, but, 

 since this species was not taken below 150 fathoms, its occurrence 

 in maximum abundance in from 25 to 75 fathoms between noon 

 and 2 p.m. and in minimum abundance between 2 and 4 p.m. 

 suggests that upward migration from these depths begins early 

 in the afternoon. 



These facts, while they do not prove that intense light causes 

 downward and subdued light upward migrations, certainly point 

 strongly in this direction. 



Before leaving this question of the effect of light on the dis- 

 tribution of this species, it is well to consider evidence obtained 



