SEA-FISHERIES LABORATORY. 



377 



until May 10th, and the numbers had dropped again by 

 June 12th, and the maximum haul was only 69,982,500 

 on May 16th. So that, whereas last year we were able to 

 show the rise and fall of the Diatom vernal maximum 

 in a table (p. 133 in the last Report) giving the numbers 

 throughout May and the first week of June, this year we 

 should need to give them for the four months March to 



$00,000 Dioit 



2,000 Di.no: 



l,OOOCopef>-- 



Jan. Feb. Mar. Apr. May June July Aug. Sept. Oct. Nov. Dec. 



Fig. 2. — Curves for chief groups and total plankton of vertical net in Bay. 



June in order to cover the period of the Diatom visitation. 

 On analysing the vernal maximum into its 

 constituent factors, it is found that species of Chaetoceras 

 and Rhizosolenia are enormously more abundant than 

 any other forms, and that the former is present in 

 greatest quantity in March and April and the latter in 



