204 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



16th is most rapid. The most abundant species were 

 Chaetoceras debile and Ch. sociale. On May 16th the 

 first of these species reached 30,000,000, and the second 

 12,000,000 per haul. 



The More Important Genera of Diatoms. 



We have taken out again the same seven genera 

 as in our last report, viz., Biddulphia, Chaetoceras, 

 Coscinodiscus, Rhizosolenia, Thalassiosira, Guinardia 

 and Lauderia. 



We think it unnecessary to print the detailed tables 

 again this year. Those we gave last year (Part IV, pp. 

 204-6) form a very good example, and we shall merely 

 note here the points in which the details for each of the 

 seven genera differ in 1911 from those recorded for 1910. 



Biddulphia. — Does not attain to quite such high 

 numbers in spring this year, and the highest record 

 (312,560) is in April in place of March ; but after dying 

 out completely in summer, the genus has a second, and 

 this year a greater, maximum in November (660,600 on 

 November 24th), when there is the high monthly average 

 of 341,231— last year it was under 40,000. 



Chaetoceras. — Last year the maximum of this genus 

 (49 millions) was in April. This year it is a month later 

 with 68 millions on May 16th. The autumnal, smaller 

 maximum is larger than in the previous year, and reaches 

 over 10 millions on October 2nd, and about 6 millions on 

 October 16th and 19th. 



Coscinodiscus. — The spring maximum was earlier 

 this year than in 1910, and reached 392,400 on March 

 14th. An unusually late haul was 79,290 on May 1st. 

 The autumn increase was unusually great, the maxima 

 being 42,400 on October 10th, 44,700 on October 16th, 



