1914] Esterly: Ctenophora of the San Diego Region 29 



Table 5 considers the distribution of Pleurohrachia for the sum- 

 mer months with regard to temperature, giving the total number of 

 hauls, the number of successful hauls and the total number of animals. 

 Temperatures below 16.1° are not included because, as may be seen in 

 table 4, no hauls were made at those points in the months considered. 



The number of animals obtained in August is many times greater 

 than in any other month, and temperatures above 19 ?1 are character- 

 istic and more favorable for the species than in any other month. It 

 seems plain, however, that temperature is not to be considered alone, 

 for during July there were almost as many hauls at high temperatures 

 as during August; yet the animals were rare. During October also, 

 more collecting was done than in August at temperatures that would 

 seem to be most favorable (judging by numbers of specimens ob- 

 tained) during the latter month, but all the October hauls were un- 

 successful. Some other factor, which does not appear in our data, is 

 surely concerned, for otherwise the numbers of animals taken in July 

 and October should at least approach those in August. If the pre- 

 vailing temperature makes the season, July and October ought to be 

 as favorable as August. 



The other factor undoubtedly stands in some relation to the ap- 

 pearance of the large animals as already set forth, but I cannot say 

 more than this at present. 



In table 6, which follows, there is a summary of the relation be- 

 tween abundance of Pleurobrachia and temperatures when all the 

 summer hauls are combined. The prevalence of the animals at high 

 temperatures is strikingly shown, though it should not be forgotten 

 that the August collections furnish most of the animals and a large 

 proportion of the successful hauls. 



TABLE 6 



Distribution of Pleurohrachia at the Surface With Regard to Temperature: 



Summer Months 





Temperat 



ure 



No. 

 Total. 



of hauls: 

 Success. 



No. 

 Total. 



of hours : 

 Success. 



No. 

 Total. 



of animals : 

 Per hour. 



Frequency : 

 Haul. Time, 



1. 



17° and ; 



less 



30 



2 



23.6 



0.8 



9 



0.4 



7 



3 



2. 



17?1-18° 





28 



2 



24.8 



1.3 



2 



0.08 



7 



5 



3. 



18?1-19° 





25 



6 



19.4 



4.5 



371 



24.1 



24 



22 



4. 



19?l-20° 





31 



13 



33.4 



9.6 



4119 



130.4 



37 



25 



5. 



20 ?1 and 



more 



38 



14 



24.7 



10.4 



2577 



115. 



31 



38 



