376 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



this year, and the vernal maximum seems to be spread 

 over a great length of time. In 1912 the smaller but 

 quite decided autumnal maximum is in September, and 

 is greater than in 1911 (23"4 c.c. as against 153 c.c). 

 The Diatom maximum is a month later and nearly twice 

 the bulk of that in 1911, but this is wholly due to the 

 enormous quantities of Rhizosolenia taken in June ; 

 nearly 41 millions of the 47 millions in the table being 

 due to Rhizosolenia. The well-marked Dinoflagellate 

 maximum is in May (June in 1911), and is unusually 

 high. The Copepoda reach their maximum at an 

 unusually early date, at least a month before that of 

 1911, when the highest numbers were in July and 

 August, while this year they are in May and June. 



The table above and the remarks following it apply 

 to the double hauls of the horizontal tow-nets; while the 

 diagram below (fig. 2) represents the curves for total 

 plankton, Diatoms, Dinoflagellates and Copepoda as 

 captured in the vertical net at the mouth of the Bay. 

 On the left-hand margin the volume in c.c. of the total 

 plankton, and the separate scales for Diatoms, Dino- 

 flagellates and Copepoda, respectively, are indicated. 



The general correspondence with the results 

 obtained from the much larger catches of the horizontal 

 nets will be noticed. 



Diatoms. 



Compared with the previous year, the appearance of 

 Diatoms in quantities in the spring of 1912 was earlier. 

 Nearly 2 millions was reached in the double haul as early 

 as March 11th, and nearly 25 millions on March 21st, 

 and these high numbers were sustained until the middle 

 of June, the actual maximum being 202,993,600 on 

 May 30th; whereas in 1911 millions were not reached 



