114 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



of July Lad its stomach packed full with Pleurobrachia in 

 various stages of digestion. At the lower end of the stomach 

 the organisms were quite broken down into a soft granular 

 reddish coloured mass. At the upper end and in the oesophagus 

 the Pleurobrachia were almost entire. They were easily recognis- 

 able. A few second stage larvae of Nephrops were invariably 

 mixed with the Pleurobrachia. Clupeoid and Polychaet remains, 

 Calanus and Temora, and the amphipod Hyperia were also 

 occasionally noticed. While ctenophora were abundant, and 

 formed the food supply of the mackerel off Walney, quite a 

 different state of affairs was prevailing round about Mull, 

 where Professor Herdman happened to be with his S. Y. 

 " Kuna." In a letter from Tobermory Bay, dated July 12th 

 and published in " Nature " on July 17th, he writes " On 

 arriving in the bay last night we found the local boats had been 

 catching abundance of mackerel close to. We bought some for 

 supper (good fish for a halfpenny each), and on dissection 

 found that the stomachs of all of them were crammed full of 

 fresh-looking Calanus (the individual copepods for the most 

 part distinct and perfect), along with a few immature 

 Nyctiphanes and larval decapods." A sample of the plankton 

 was taken later on in the evening and an ordinary coarse tow- 

 net caught 20 c.c. of the copepoda in five minutes which was 

 estimated to contain 6,000 Calanus. Professor Herdman 

 found that the stomach contents of a single mackerel contained 

 about the same amount of Calanus as the tow-net caught in 

 five minutes. 



The invasion of Pleurobrachia began to die away in the 

 area off Walney about the middle of July, and although it 

 continued a conspicuous object in the stomach contents, a 

 more mixed diet was gradually making its appearance. The 

 mixture was rather different from what was observed at the 

 end of June. The copepoda were represented by Calanus and 

 Temora only. The Cladocera Evadne and Podon were now 



