278 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY 



to regard these two peaks as unusual, and if they be 

 removed the Copepod curve shows a gradual rise during 

 May and June. 



The Diatom and Dinoflagellate maxima appear about 

 the same time at Stat. Ill, and are in the surface 

 gatherings (April 13th), before they appear (Diatoms on 

 April 17th, and Dinoflagellates on the 19th) in the hauls 

 from 20 to 10 faths. It is not possible to compare the 

 actual volumes in these 20-10 vertical Nansen-net hauls 

 with those of the horizontal, 15-minutes, tow-net. The 

 relative volumes and the daily and monthly variations 

 may, however, be compared. 



The Diatom and Dinoflagellate maxima extend into 

 May. The Diatom maximum ends between May 24th and 

 May 28th. The Dinoflagellates are relatively more 

 abundant than the Diatoms in May and June. 



Diatoms and Dinoflagellates, like the Copepoda, 

 decrease rapidly in numbers about April 9th, after fine 

 weather. 



Although the Dinoflagellate rise begins only a day 

 or two after that of the Diatoms in the second half of 

 April, the numbers of the Dinoflagellates keep up better 

 and are relatively greater than those of the Diatoms in 

 June. 



The end of the Diatom maximum before May 28th, as 

 well as the fall in the amount of plankton on April 9th 

 and April 23rd, is shown by the Nansen vertical hauls as 

 clearly as by the horizontal surface nets. 



The lYansen net hauls show the Diatom maximum, 

 throughout the water down to 20 faths., to extend from 

 April 19th to May 24th. During the latter part of May 

 and in June the Diatoms decrease in these vertical hauls 

 and the Dinoflagellates increase. On June 1st there are 

 actually more Dinoflagellates present than Diatoms. 



