144 University of California Publications in Zoology [Vol. 13 



(c) The Nansen nets obtained over 1100 specimens of Euphausia, 

 and more than 1000 of these in March and April, but only eleven 

 specimens of Nyctiphanes were present in the entire series of Nansen 

 hauls. 



(d) The center of the sub-surface region where Euphausia is more 

 abundant by day, as shown by the winter hauls, appears to be at 300 

 meters, while Nyctiphanes seems to center at 150 meters during the 

 day. 



(e) There is some evidence that both Euphausia and Nyctiphanes 

 perform diurnal migrations. 



(/) Euphausia is more abundant at the surface in the summer, 

 and Nyctiphanes in the winter, but both are found in larger numbers 

 (in the respective seasons) when the surface temperature ranges from 

 16?1 to 17°. 



(g) Nyctiphanes is found in much larger numbers (at the surface 

 and during the winter) between 4 and 6 a.m. than at any other period 

 of the day. No specimens were found between 10 a.m. and 4 a.m. 

 The time of greater abundance of Euphausia at the surface (during 

 the summer) is from 6 to 8 p.m., but this appears from only six suc- 

 cessful hauls. 



(h) A comparison of the manner of occurrence of Euphausia with 

 that of Nyctiphanes suggests that species may be characterized by 

 behavior as well as by structure. 



Occidental College, Los Angeles, California. 

 Transmitted February 6, 1914. 



