282 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Dinoflagellate curve is consistently a month later and 

 reaches its climax in June, while the Copepods have two 

 small elevations in March and June and a much greater 

 peak in September-October. In '09 the Diatom record is 

 peculiar, since there seem to be two spring maxima, April 

 and June, while the Dinoflagellate maximum is in May 

 to June and the Copepoda in July and August. 



, Consequently, in all three years the order of 

 succession of the vernal maxima is the same, and when the 

 nine curves are placed together on a sheet, although there 

 is of course some overlapping, the Diatoms form an earlier 

 and the Copepoda a later group, while the Dinoflagellates 

 lie between. 



The autumnal maxima are much less definite. The 

 Copepod rise in September-October is the most marked 

 and most regular, the Diatom increase is much less 

 marked than that in spring and is less regular in its 

 appearance, while the Dinoflagellate increase, if there is 

 one, is still less marked and less constant. 



Important Genera of Diatoms. 



Last year we took out the five leading forms, 

 Biddulphia, Chcetoceros, Coscinodiscus, Rhizosolenia, 

 Thalassiosira, for separate consideration; this year we 

 add a sixth, Guinardia. The first point that one remarks 

 in comparing the records for the two years is the close 

 agreement in distribution throughout the year in some of 

 the cases. In both years Biddutyhia begins with 4 

 figures in January, works up io 6 figures in April, dies oft' 

 to nothing at the end of May (May 20th in '08, May 27th 

 in '09), reaches 4 figures again suddenly on September 

 14th (1,180 in '08, 1,200 in '09), and remains present in 

 thousands until the end of the year. The numbers 

 become greater, however, towards the end of this year 



