bb TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



In all, about 400 samples have been collected from Port 

 Erin and the neighbourhood during the year, in addition to 

 those from other parts of the Irish Sea. A detailed account 

 of the plankton results will be given, as usual, by Mr. Scott 

 and myself in the Lancashire Sea Fisheries Laboratory Eeport. 



Last year (1912) the plankton hauls in the Irish Sea were 

 exceptionally large, some nettings in April containing as many 

 as 36 millions of one species and 44 millions of another species 

 of the diatom genus Chaetoceras, while one haul on May 30th 

 contained over 107 millions of Rhizosolenia shrubsolei. In the 

 present year (1913) the numbers generally were lower, and no 

 exceptionally large hauls were obtained. The diatom maximum 

 was in May and was largely composed of 3 species of Chaetoceras 

 (C. debile, C. sociale and C. teres). The genus Thalassiosira, 

 which appeared in April at Port Erin, increased to 6 J millions 

 per haul by the middle of May and died off a month later in 

 June. 



Rhizosolenia was the chief diatom present in June and July, 

 beginning with R. shrubsolei which was replaced later by 

 R. stolterfothi. In the September maximum the chief diatoms 

 were Chaetoceras decipiens, C. debile and C. densum. 



The summer maxima of both the Copepoda and the 

 Dinonagellata occurred in July. 



Early in July there was a great visitation of the Ctenophore 

 Pleurobrachia pileus (see fig. 20) all along the Lancashire coast ; 

 and Mr. Scott found that a sample of mackerel caught on 

 July 8th off Walney Island contained nothing but Pleurobrachia 

 in the stomachs. A fortnight earlier in the same region the 

 mackerel were feeding mainly on Copepoda, one examined 

 having a pure gathering of Temora, while others had Sagitta, 

 Oikopleura and larval decapods. It is evident that fish like 

 herring and mackerel although they may be attracted by some 

 special organism, like Calanus, are able to a considerable extent 



