1914] Esterly: Schizopoda of the San Diego Region 129 



TABLE 4 



Number of Hauls, Haul Frequency and Numbers of Animals for Each Month; 



Surface Collections 





Total 

 Hauls 



17 



Succ. 

 Hauls 







Freq. 

 





Numbers of animals 



A 







Month 



Feb. 



Euphausia 

 pacifica 







Nyctiphanes 

 simplex 







Thysanoessa 

 gregaria 







Nematoscelis 

 difficilis 







Total 

 



March 



30 



3 



10 



4 











1 



5 



April 

 June 



13 



83 



1 



7 



8 

 8 



1 



12.5 





 





 







1 



1 

 126 



July 

 August 

 Sept. 

 Oct. 



40 



42 



6 



20 



1 

 4 

 

 1 



2.5 

 9 

 

 5 



60 

 

 

 







10 







2 





 9 

 

 





 

 

 



60 



19 







2 



Nov. 



6 



2 



33 



1 



68 











69 



Dec. 



17 



13 



77 



6 



484 



1 



1 



492 



Schizopods were found in 32 of the 274 surface hauls. This is 

 the smallest proportion of successful hauls for any of the groups of 

 organisms that have been studied here. The chaetognath Sagitta 

 hipunctata was found in 70 per cent of the surface hauls (Michael, 

 1911, p. 115), the copepod, Calanus finmarchicus in 57 per cent 

 (Esterly, 1912, p. 281) and the ctenophore Pleurobrachia hachei, in 

 25 per cent of all the hauls (Esterly, 1914b, p. 25) . In contrast to such 

 figures as these, the schizopods as a group were found in but 12 per 

 cent of the surface hauls. 



As shown in the table, Euphausia was far more abundant at the 

 surface in June and July, and Nyctiphanes in November and Decem- 

 ber, than at any other season of the year. The frequency is exceed- 

 ingly low for all months except November and December, when the 

 occurrence of Nyctiphanes makes the number of successful hauls large 

 by comparison. The question at once arises, how much dependence 

 can be placed on a study of this sort when it has to be based on such 

 a small number of hauls that obtained animals? The answer is not 

 easy to give. We must use what evidence we have, and it may reason- 

 ably be urged that the proportion of successful and unsuccessful hauls 

 is as large now as it ever will be, since our collections extend over 

 different periods in five years. More collections will undoubtedly 

 increase the number of animals obtained and perhaps distribute the 

 hauls more evenly as to season or time of day, but it is not to be 

 expected that the frequency of occurrence will be raised. 



