SEA-FISHERIES LABORATORY. 315 



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 

 2,400 specimens of Calanus. This would give about 

 6,000 Copepods in the stomach of an average mackerel, or 

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



" 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 our summer 

 observations went : — 



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



"On getting back to Tobermory on Saturday, we 

 found the plankton to be in marked contrast to its condi- 

 tion four weeks ago. The vast swarm of Calanoids has 

 gone, and there are now no signs of mackerel feeding in 

 the bay. In fact, the change has been noticeable for some 

 days in the seas outside, and we have not been getting lately 

 the large plankton catches that were usual in the latter 

 half of July. On July 14th, a haul of the large surface 

 tow-net, in the open sea off Ardnamurchan, gave such a 

 huge catch of Calanus (about 1,000 c.c.) that we promptly 

 took a second similar haul, and had it cooked as a sort of 

 potted ' shrimp' confection for tea (sampled by ten persons, 

 including the crew, who were much interested to try this 

 new edible ' fish ') ; while on August 11th a haul of the 

 same net, taken at the same spot, gave only a small catch 

 of some 15 c.c, containing very few Calanoids, along with 

 the usual scanty summer zoo-plankton." 



It will be remembered that some years ago, Dr. E. J. 



w 



