SEA-FISHERIES LABORATORY. 401 



quoted, and are known to biologists (see especially the 

 works of Heincke, Moebius, Nordgaard, Pouchet, Murray 

 and Hjort). 



Then as to demersal fish — young plaice, after their 

 metamorphosis, feed chiefly on Copepoda, while in 

 younger stages the larval plaice feeds upon Diatoms. 

 We have found at Port Erin the post-larval plaice with 

 its stomach shining through of a golden-brown colour 

 from the Diatoms with which it was filled, and one of us 

 has watched in a shallow pond the metamorphosed small 

 plaice darting backwards and forwards pursuing, 

 catching and devouring the individual Copepoda. Then 

 again it has been shown that these Copepoda in their 

 turn feed on Diatoms, Dinoflagellates and Protozoa. So 

 practically all the main constituents of the plankton are 

 concerned in the nourishment of either young or adult 

 fishes. 



On the Lancashire coast we find the young plaice 

 which are just appearing in the inshore nurseries have 

 their stomachs filled with pelagic larval annelids. 



The Pollan (Coregonus pollan) of Lough Neagh, in 

 Ireland, has been shown to be on some occasions filled 

 up with Mysis relicta, and at other times to be feeding 

 solely on Cladocera ; and there is reason to believe that 

 the movements of the fish, which are extensive and 

 periodic, can be definitely related to the presence and 

 nature of the plankton. 



Dr. Hjort has shown a correspondence between the 

 distribution of the plankton-feeding whales (such as the 

 Greenland whale) and the most abundant swarms of 

 plankton at particular seasons. Prof. G. 0. Sars and 

 others, in tracing shoals of herring and cod in the North 

 and West of Norway, have distinguished between the 



