376 



TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Lauderia. — The maximum is only 601,000 on 

 May 16th, and the highest autumn number is only 8,500 

 on September 22nd. 



Asterionella. — This is a genus which has been repre- 

 sented in the past, so far as our observations show, by 

 comparatively small numbers of the species A. bleaJceleyi; 

 but this year, in addition to a few thousands of that form 

 in April and May, enormous numbers of a second species, 

 A. japonica, appeared for quite a short period in the 

 middle of May, and reached 192 millions in one haul on 

 May 16th. 



We add here the table showing the monthly averages 

 of the usual seven genera of Diatoms, together with an 

 eighth, Asterionella, which was unusually prevalent this 

 year. 



1913. 



Biddul- 



Chaeto- 



Coscino- 



Rhizoso- 



Thalassi- 



Guin- 



Laud- 



Asteri- 





phia. 



ceras. 



discus. 



lenia. 



osira. 



ardia. 



eria. 



onella. 



Jan. 



. 15,925 



3,142 



3,167 











105 











Feb. .. 



. 27,860 



8,349 



19,861 



111 







51 



74 



300 



Mar 



. 29,487 



252,685 



86,631 



94 



187 



1,087 



580 







April . . 



. 31,645 



2,677,396 



195,325 



3,875 



28,494 



14,206 



24,750 



665 



May .. 



6,822 



2,967,283 



19,847 



129,178 



898,589 



78,089 



109,144 



22,685,144 



June . . 







362,237 



756 



1,663,669 



37,169 



945,387 



1.452 



125 



July .. 







37,075 







2,574,350 







655,740 











Aug. .. 







39,636 







53,646 







827 











Sept. .. 



374 



177,216 



6 



3,803 







3,939 



1,129 



1,100 



Opt. .. 



1,626 



6,579 







40 







250 



3 



10 



Nov. . . 



6,383 



74,086 



4,996 



19 



7 



259 











Dec. .. 



. 13,117 



6,421 



8,266 



138 







432 







5 



This table probably gives quite as clear a picture as 

 we could get from a series of curves to show (1) the waxing 

 and waning of the different generic groups throughout the 

 year, and the manner in which, for example, Rhizosolenia 

 is at its maximum just when Biddulphia shows a mini- 

 mum ; and (2) the characteristics of each month, beginning 

 with a scanty phyto-plankton of Biddulphia, Chaetoceras, 

 and Coscinodiscus in January, working up to the maximum 



