194 PROF. 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 I 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 five-minutes’ haul of the tow-net, on this occasion. 
Fie. 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, 
* [t may be added that these mackerel were evidently not being nourished 
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in accordance with the views of Piitter, and were clearly able to fill their 
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stomachs from the plankton around them.”. 
The following note, written some weeks later, records the conclusion of the 
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matter, so far as that summer’s observations went :— 
“S.Y. ‘Runa,’ off Island of Eigg, August 12th, 1913. 
* On getting back to Tobermory on Saturday, we found the plankton to be 
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in marked contrast to its condition four weeks ago. The vast swarm of 
I2] 
