OF DIATOMS AND COPEPODA IN THE IRISH SEA. 195 
Calanids has gone, and there are now no signs of mackerel feeding in the 
bay. In faet, 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 1000 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 Calanids, along with the usual scanty summer 
zooplankton.” . . .. 
The importance of Calanus as a food for migratory pelagic fishes such 
as the mackerel cannot be doubted (see fig. 14). 
PsSEUDOCALANUS. 
Pseudocalanus elongatus (Boeck) is widely distributed in the North Atlantic 
and is present in the Irish Sea throughout the year (fig. 15). It reaches its 
lowest level in January and February, and has its maximum in late summer 
and autumn (June to October in our records, generally September or October). 
Fra. 15.— Pseudocalanus elongatus, from a photo-micrograph by A. Scott. 
This Copepod comes next after Oithona as the second most abundant 
species in the Irish Sea, its average per haul over the ten years being 4583. 
Some of the most important records are :—65,200 on May 20th, 1912 ; 
91,960 on October 21st, 1912 ; 68,120 on June 24th, 1913 ; 60,600 on May 
5th, 1916 ; 59,600 on September 25th, 1916 ; 58,200 on October 31st, 1912; 
54,350 on July 31st, 1911; and many other records between 35,000 and 
50,000 in these same months. 
