SEA-FISHERIES LABORATORY. 105 



years, and the monthly average haul was 61-8 c.c. — the largest 

 actual haul (= coarse and fine nets combined) being 175 c.c. 

 on June 16th. The amount of the catches during that month 

 was, however, much increased by the quantity of Halosphaera 

 present. In 1915 when the highest monthly average was 

 63-5 c.c, in May, the bulk of the largest catches was also due 

 to Halosphaera. 



The Diatom maximum in 1916 was in May when the 

 monthly average in estimated number of individuals per haul 

 was over seven millions, the actual greatest haul being 

 24,260,800 Diatoms (mainly Chaetoceras) on May 25th. 



The autumnal maximum was again very slightly marked, 

 although rather larger than in the previous year. The monthly 

 average reached 11-3 c.c. in September, as against an autumnal 

 maximum of 8-9 c.c. for October, 1915. 



Again there were no vast swarms of Diatoms this year 

 in the district. There were particularly few members of the 

 genera Rhizosolenia, Guinardia and Lauderia. By far the 

 most abundant forms were species of Chaetoceras — amounting 

 to about 25 times as many as those of any other genus of 

 Diatoms. 



The maxima of the leading groups succeeded one another 

 in the usual order, as follows : — 



In May, the Diatom maximum. 

 [In June, the Total plankton maximum.] 

 In July, the Dinonagellate maximum. 

 In September, the Copepod maximum. 



The monthly average number of Dinoflagellates for 

 July was 148,241, the actual largest number being 316,400 on 

 July 6th, and of these 300,000 were Ceratium tripos which 

 as usual was much more abundant than the species of Peri- 

 dinium. These Dinonagellate numbers are rather higher than 

 those for 1915. 



