SEA-FISHERIES LABORATORY. 379 



but after that date the numbers dropped suddenly, and 

 in June the genus was entirely absent. It appeared 

 again in the middle of September, and rose to a second 

 maximum of 35,000 on October 7th. 



Rhizosolenia. — This genus was present in enormous 

 quantities from the middle of May to the middle of June, 

 and was much more abundant than we have ever known 

 it before. The two highest records are 184 millions on 

 May 30th and 173 millions on June 3rd — per standard 

 haul in every case quoted. After dying down in the 

 middle of July, Rhizosolenia was again present from 

 September 13th for about a month, the highest haul being 

 647,000 on September 30th. 



Thalassiosira. — There was one large haul of over 

 6 millions on April 29th, but the next highest was only 

 289,300. In 1911 the maximum was not until the end 

 of May, by which time this year the genus had entirely 

 disappeared. Its appearance in autumn was also earlier 

 this year, but the numbers only reached 28,000 

 (September 30th), as against 287,000 on October 5th, 

 1911. 



Guinardia. — This genus is unusually abundant this 

 year, very high numbers being met with throughout May 

 and June, and the maximum being 22,800,000 on 

 June 3rd ; 70,000 on September 30th is the highest record 

 for the autumn. 



Lauderia. — This form is more abundant than in 

 1911, but not so abundant as in 1910. The maximum is 

 12^ millions on April 29th, but only on that occasion did 

 the numbers reach the millions. 



We give here the monthly averages of these seven 

 genera of Diatoms, as follows: — 



