374 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Biddulphia. — This genus is again, as in 1912, repre- 

 sented by a few thousands and tens of thousands only from 

 January to May, and by rather smaller numbers from 

 September to December. It is entirely absent in June, 

 July, and August. In the three years previous to 1912 

 the numbers reached six figures at the time of the spring 

 maximum, but in 1912 the maximum was only 88,240 

 (March 11th), and this year only 90,750 (April 24th) ; and 

 this year the secondary maximum was much smaller and 

 later than in any of the other years, reaching only 20,800 

 on December 5th. 



The above figures represent both species, B. mobiliensis 

 and B. sinensis, taken together. B. sinensis, as usual, does 

 not make its appearance until late in November, while 

 B. mobiliensis is frequent from September onwards. Both 

 species continue to be represented throughout the spring 

 and early summer, but B. mobiliensis is generally in con- 

 siderably larger quantities. 



Chaetoceras. — In the last three years this genus was 

 present in enormous quantities in spring (nearly 95 

 millions on April 29th, 1912), and had also a high autumn 

 maximum (nearly 30 millions in 1912). This year, 

 although still the most abundant Diatom in the plankton, 

 the numbers are not nearly so high, and the highest record 

 is only 7,422,000 on April 7th, while in September the 

 numbers only reach 857,500 on the 18th. The monthly 

 average for May is, however, slightly higher than that for 

 April — between two and three millions in each case. 



Coscinodiscus. — The genus was well represented during 

 the first six months of the year, starting with a few 

 thousands in each haul in January, reaching 500,000 (the 

 maximum) on April 7th, with the monthly average for 

 April nearly 200,000, dropping to a few thousands again 

 at the end of May, and to a few hundreds at the end of 



