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FROF. W. A. HERDMAN ON THE DISTRIBUTION 



The mackerel were obviously darting about, occasionally leaping to the 

 surface (which gave the gulls their opportunity) where the whirls, caused by 

 the Copepoda, were thickest, and an examination of the stomach-contents of 

 the fish on the yacht afterwards, showed us that the amount in one mackerel 

 was about the same quantity as that caught, by the tow-net in five minutes. 

 Professor Newstead and 1 have made a count of 8 c.c. of the tow-net 

 gathering, and estimate that it contains about 2400 specimens of Calanus. 

 This would give about 6000 Copepods in the stomach of an average mackerel, 

 or in a rive-minutes' haul of the tow-net, on this occasion. 



FiG. 14. — Photograph of exceptionally large hauls (about 1000 c.c. in a 

 jar) of Calanus taken from the yacht 'Runa' in 1913 on the west coast 

 of Scotland. The largest haul was estimated to contain at least 

 half a million individuals. 



" It may be added that these mackerel were evidently not being nourished 

 in accordance with the views of Putter, and were clearly able to fill their 

 stomachs from the plankton around them.'". . . . 



The following note, written some weeks later, records the conclusion of the 

 matter, so far as that summer's observations went : — 



" S.Y. ' Runa,' off Island of Eigg, August 12tb, 1913. 



" On getting back to Tobermory on Saturday, we found the plankton to be 

 in marked contrast to its condition four weeks ago. The vast swarm of 



