178 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Biddulphia and Coscinodiscus, have their spring maximum in 

 March, other two, Rhizosolenia and Guinardia, in June and 

 the remaining three, Chaetoceras, Lauderia and Thalassiosira, 

 in May. An unusual though not unprecedented feature is to 

 find that Biddulphia attains to higher numbers in November 

 than at the spring maximum. 



Another unusual feature this year is the relative scarcity 

 of the large Copepod Calanus finmarchicus which in place of 

 invading the bay in quantity in July as it has done in previous 

 years was in 1919 very poorly represented. The only catch 

 above 1,000 was 1,240 on June 5th. Pseudocalanus elongatus 

 was on the other hand more abundant than last year and was 

 present in quantity from May till November. The highest 

 record was 36,340 on June 9th. Oithona similis was also 

 unusually abundant, and at its maximum in June and July 

 gave nine hauls of over 50,000, the highest being 115,280 on 

 July 31st. The six important genera Calanus, Pseudocalanus, 

 Temora, Centre-pages, Acartia and Oithona all show maxima 

 in June, while Paracalanus has its maximum in September. 



In view of the enormous quantities of Noctiluca that 

 Mr. Scott obtained in the Barrow Channel in December it is 

 interesting to notice that at Port Erin the numbers were 

 comparatively low, the largest hauls (up to 26,200) were in 

 July, and some months of the year in both spring and autumn 

 showed none at all. 



The other chief organisms of the plankton — Oikopleura, 

 Sagitta, Cladocera, Medusae, Ctenophora and the various 

 groups of larvae — have not shown any special features in their 

 occurrence during 1919, but corroborate more or less exactly 

 the conclusions arrived at in previous years. 



Phyto-plankton in Relation to Fish LARViE. 

 We drew attention in last Report to the very small number 

 of different kinds of organisms — both plants and animals — 

 that make up the bulk of the plankton that is of real importance 



