284 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



after which, the species is unrepresented. If, as seems 

 possible, we had in '07 an immigration of the northern 

 species Thalassiosira nordcnshioldii, the numbers seem to 

 be gradually diminishing. 



Guinardia, unlike the last two genera, is present 

 throughout the year. It works up from small numbers to 

 1,000 in April, 20,000 in May, and to a few millions in 

 June— 1,500,000 on June 9th, 3,000,000 on June 12th, 

 4,000,000 on June 15th, and 3,500,000 on June 22nd— 

 after which the numbers gradually fall to thousands in 

 July to September, hundreds in October and November, 

 and tens in December. In '08 the maximum was at the 

 same point, and the general course through the year was 

 similar ; but it did not appear in our gatherings until the 

 middle of April — there were usually 1,000 to 4,000 during 

 the rest of the month. In May it reached 50,000 on 20th, 

 and 100,000 on 30th. The numbers were half a million on 

 June 4th, and the maximum of nearly a million, twice, 

 towards the end of the month. Then the numbers fell 

 rapidly to thousands in July, hundreds in August to 

 October, and tens in November and December — a very 

 similar record to that of the present year. 



According to Lohmann, at Kiel, Sceletonema, which 

 is one of our rarer forms, is the commonest Diatom, and 

 attains its maxima in May-June and September-October. 



BlDDULrHIA SINENSIS IN PORT ERIN BAY, 1909. 



This species of Diatom was first noticed in our bay 

 gatherings of November 9th, '09, when 400 specimens 

 were counted in the gathering from the coarse net and 

 40 from that of the fine. In the following haul on 

 November 13th about four times the quantity was present, 

 1,600 in the coarse and 200 in the fine ; and during the 

 remainder of the year to December 17th numbers varying 



