290 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Chaetoceras debile, of which there were 148 millions 

 present in the double haul. It may be recalled that the 

 previous year (1913) it was another species, Asterionella 

 japonica, that was present in great abundance, running 

 up to nearly 200 millions per haul on May 16th. In 1913 

 the vernal phytoplankton at Port Erin was an 

 " Asterionella-plankton," in 1914 it was a " Chaetoceras- 

 plankton." We pointed out last year the probability 

 that amongst the competing common spring Diatoms 

 some slight advantage enables sometimes one form and 

 sometimes another to gain the mastery and become for 

 a short time enormously abundant. 



The More Important Genera of Diatoms. 



We give here our usual short summary of the 

 distribution throughout the year of the more important 

 Diatoms. 



Biddulphia. — The spring maximum (78,100 on 

 March 30th) was again low, as in the two previous years, 

 but the autumn figures resemble closely those of 1911 

 when there was the unusually high maximum of 660,600 

 on November 24th; this year we have 800,400 on 

 November 3rd. These are the only two years of our 

 investigation in which the autumn maximum has been 

 higher than the spring maximum. This includes the two 

 forms B. mobiliensis and B. sinensis, of which sometimes 

 the one and sometimes the other is the more abundant. 



Chaetoceras. — This was again by far the most 

 abundant Diatom in the plankton, and is represented in 

 our gatherings throughout the year. The spring increase 

 began early in March, the numbers reaching to over a 

 million before the end of the month. On April 30th we 

 had 10,443,500, and on May Tth 10,207,200, while the 

 maximum occurred between those dates with the 



