378 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



May and June. From the middle of May to the middle 

 of June the bulk of the catch is composed of Rhizoso- 

 lenia, but Guinardia is also represented by numbers of 

 from 1\ millions to nearly 23 millions, and these two 

 genera (along with a few tens of thousands of Chaetoceras 

 and a few Eucampia) are the only Diatoms found in our 

 nets in June. 



The autumnal maximum was a few weeks earlier in 

 1912, and was higher; as in previous years, it consisted 

 mainly of a few species of Chaetoceras. 



The More Important Genera or Diatoms. 



We shall again pick out the more salient features in 

 the distribution throughout the year of the same seven 

 genera of Diatoms dealt with in previous reports. 



Biddulphia. — This genus is represented, by a few 

 thousands and tens of thousands only, from January to 

 the middle of May, and again from the middle of 

 September to the end of the year. The highest record is 

 88,240 on March 11th, and in autumn the highest is 

 69,960 on November 14th. These numbers are consider- 

 ably lower than those for 1911. [See note (p. 380) on 

 the species or " forms " of Biddulphia present.] 



Chaetoceras. — The maximum this year is at the end 

 of April with 94,733,000 on the 29th, 26 millions more 

 than the maximum of 1911 (on May 16th). The 

 autumnal maximum also is greater, with 29f millions 

 on September 26th, as against 10^ millions on October 

 2nd, 1911. 



Coscinodiscus. — The numbers are rather higher this 

 year than in 1911, the highest record being 462,750 on 

 March 21st, and the highest monthly average 100,619 for 

 April. On May 9th there was a large haul of 119,600, 



