1914] Esterly: Schisopoda of the San Diego Region 143 



Nine of the ten specimens of Thysanoessa taken at the surface were 

 obtained in August, and eight of the nine appeared in hauls made 

 between 4 and 6 a.m. The temperatures of the successful hauls range 

 from 19?8 to 20?1; these are two or three degrees higher than the 

 optimum temperatures for Euphausia and Nyctiphanes. 



Thysanoessa appeared in the Kofoid nets only in November and 

 December; there were six animals and five of them were taken at 

 depths between 55 and 73 meters, while one was in a haul at 185 

 meters. All of these are daj^ hauls and it seems, therefore, that this 

 species does not go as deep as the two commoner ones. One specimen 

 was obtained in the Nansen nets, in December, and in a haul from 

 46 to 37 meters. 



Two specimens of Nematoscelis were obtained at the surface, one 

 in June and one in December. Twenty animals were taken with the 

 Kofoid net, none above 73 meters nor below 185 meters ; eleven of the 

 specimens came from between 137 and 185 fathoms. All but one of the 

 animals were obtained during the winter. The successful hauls with 

 the Nansen nets were made in March and April. Only one of the 

 seventeen specimens was obtained from above 185 meters, while eleven 

 came from below 365 meters. This range is much below that shown 

 by the Kofoid nets. 



SUMMARY 



1. The Schizopoda as a group are found in smaller numbers and 

 less frequently than the Chaetognatha, Copepoda, or Ctenophora. 



2. The Schizopoda are obtained in much greater numbers during 

 the colder season of the year (November-April) , and especially in 

 December, February and March. 



3. Euphausia pacifica Hansen and Nyctiphanes simplex Hansen 

 are the more abundant species, and the ones whose behavior is better 

 known. With regard to these two forms, we find: 



(a) Euphausia is more abundant at the surface in June and July,, 

 while Nyctiphanes is more abundant during November and December. 



(6) Both are obtained with the Kofoid net in larger numbers in 

 December; these hauls are practically unsuccessful during the other 

 months. 



