424 University of California Publications in Zoology t v ° L - 22 



the results are due to such a cause. The probabilities were determined 

 from results corrected by the ratio of the means and by the means of 

 the ratios, but only the averages are given in this paper. 



On the whole the copepods were considerably more abundant 

 during the second year. The totals in round numbers for the two 

 years and for each year separately were as follows: Acartia tonsa, 

 total 248,000 ; 86,000 the first year, and 162,000 the second ; A. clausi, 

 total 475,000; 182,000 the first year, and 293,000 the second; small 

 calanids, total 330,000 ; 184,000 the first year, and 146,000 the second ; 

 Podoplea, total 4,350.000; 1,210,000 the first year, and 3,140,000 the 

 second. The mean annual abundance, as given in tables 2 and 5, 

 shows that all the forms except the small calanids were found in 

 larger numbers during the second twelve months. 



If we consider the corrected values for the six periods (see table 

 5) it will be noted that there is only one place (8 p.m. for small 

 calanids) where the number of animals per haul during the dark 

 hours is not greater during the second year. During the light hours, 

 however, the larger numbers per haul appear more often during the 

 first year. 



It seems evident that the mixed assemblage of genera called "small 

 calanids" constitutes a group somewhat apart from the other Copep- 

 oda in occurrence, when one year is compared with another. We 

 cannot say much more than this until the genera and species have 

 been segregated and the results tabulated. It is possible that there 

 are one or two predominant forms whose distribution determines that 

 of the group as a whole. 



The values for the mean monthly abundance of the animals show 

 results that are similar to those that are indicated by the total numbers 

 and by the distribution through the twenty-four hours. "When the 

 mean abundance for each month is compared for the two years (see 

 table 3 ) , it is seen that for nine months out of twelve the numbers of 

 A. tonsa were greater in the second year; in ten months out of twelve 

 the numbers of A. clausi were greater in the second year; in seven 

 months out of twelve and in eleven out of twelve larger numbers of 

 small calanids and Podoplea, respectively, were obtained in the second 

 year. 



The mean monthly abundance shows clearly the season of the year 

 at which the different copepods were most and least abundant. The 



