250 U)iivcrsif>j of California Fahllcations in Zoologij [Vol. IS 



Since the standardized frequency given by the above formula, 

 is that time frequency which would most probably have resulted had 

 every haul consumed the same amount of time (=one hour), it is 

 equivalent to what the haul frequency would have been under the 

 same conditions. The latter is therefore of no avail and tlie methods 

 employed in this investigation are two: (1) the average number of 

 solitary forms and aggregate forms obtained per hour under the 

 various temperature conditions are compared; and (2) their standard- 

 ized frequencies under the same temperature conditions are compared. 

 By using these two methods, the first of which is affected by variability 

 in number of individuals collected while the latter is entirely inde- 

 pendent of such variability, a check on interpretation is maintained. 



3. Brief Discussion of Seasonal Distribution 



Investigations concerning the distribution of the chaetognatha 

 (Michael, 1911, p. 139) revealed no apparent seasonal effect. Simi- 

 larly, no seasonal effect is apparent in the data discussed by Esterly 

 (1912) relative to the copepoda. In the case of Salpa democratica, 

 however, the influence of season is pronounced. As revealed by the 

 following table, both generations of this species occur on the surface 

 mainly during the months of June and July, solitary forms being 

 restricted entirely to these months. No collections, however, were 

 made during the months of January, May, October, or December. 



Table 2 



Seasonal surface distribution of Salpa democratica during 1908-09 



Number of animals 



Average Solitary forms Aggregate forms 



Hours of tempera- Average , ^ \ r ^ \ 



Month Hauls hauling ture salinity Total Per hour Total Per hour 



Feb. 5 6.3 1.3?6C 33.540/0,, 6 1 



Mar. 15 12.6 15.1 33.64 Q 



Apr. 6 4.1 16.1 33.70 



June 41 28.2 17.9 33.61 4,164 147 12,516 444 



July 35 25.5 18.9 33.64 2,592 102 2,359 93 



Aug. 15 6.5 19.9 92 14 



Sept. 6 2.3 18.5 33.88 14 2 



Nov. 5 2.6 17.9 33.85 



In addition to the almost complete restriction of both generations 

 to the months of June and July, the table shows both to have been 

 more abundant during June than during July. Moreover, while the 

 aggregate forms were more abundant than the solitary forms during 

 June, the solitary forms were the more abundant during July. This 

 difference may have been consequent upon any or all of several influ- 



