1923 J Esterly: Murine Copepoda at La J oil a 433 



4. The two years of collecting resemble each other even as to the 

 weeks when the species of Acini in were most abundant, during the 

 months when they occurred in largest numbers. (See table 4.) 



5. There is a very marked increase in abundance of all the Copep- 

 oda in the night hauls, and such differences are markedly significant 

 in the case of the two forms of Acartia. (See tables 5 and 6.) 



6. The facts obtained regarding the seasonal occurrence of Acartia 

 suggest that there is a natural and regular sequence of events year 

 after year. 



Occidental College, Los Angeles, California. 

 Transmitted February 8, 1923. 



LITERATURE CITED 

 Allen. W. E. 



1921. Preliminary statistical studies of marine phytoplankton of the San 



Diego region, California. Special Publications of Bernice P. 

 Bishop Museum, no. 7, pp. 537-554, 3 tables. 

 Esterly, C. O. 



1917. The occurrence of a rhythm in the geotropism of two species of 



plankton copepods when certain recurring external conditions are 

 absent. Univ. Calif. Publ. Zool., 16, 393-400. 



1919. Reactions of various plankton animals with reference to their diurnal 



migrations. Hid., 19, 1-83. 

 Herdman, W. A. 



1918. Spolia Runiana, III. The distribution of certain diatoms and Copep- 



oda, throughout the year, in the Irish Sea. Jour. Linn. Society, 

 Botany, 44, 173-204, 21 figures in text. 



1922. Idem. V. Summary of results of continuous investigation of the 



plankton of the Irish Sea during fifteen years. Ibid., 46, 141-170, 

 2 figures in text, 7 plates. 

 Herdman, W. A., and Scott, A. 



1908. An intensive study of the marine plankton around the south end of 

 the Isle of Man. Lancashire Sea-Fisheries Lab., report for 1907, 

 X.i. AVI, H4-197, 13 figs. 

 1912. Idem, Part V, ibid., lull, No. XX, 127-154, 5 figs. 

 Herdman, W. A., Scott, A., and Lewis. H. M. 



1915. Idem, Part VIII, ibid., 1914, Xo. XXIII, 222-240, 2 figs. 



McEwen, Gr. F. 



1920. Direct application of the idea of "random sampling" in estimating 



the precision of averages, and the significance of differences. 

 Bull. Am. Math. Soc, 26, no. 6, pp. 263 and 273. 

 Michael, E. L. 



1921. Effect of upwelling water upon the organic fertility of the sea in the 



region of southern California. Special Publications of Bernice 

 P. Bishop Museum, no. 7, pp. 555-595, 3 figs. 



