212 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



COPEPODA. 



On taking out again the records of occurrence of the 

 nine commonest species of Copepoda, we get the following 

 results : — 



Calanus helgolandicus. — As usual, Calanus was 

 present in small numbers throughout the year, but 

 became much more abundant in summer, June to 

 October, and especially in July, when two of the 

 customary large swarms appeared — one on July 4th and 

 the other on July 18th. The numbers, however, were 

 throughout smaller than in 1910. 



Pseudocalanus elongatus. — This is one of the most 

 abundant species, and is present in quantity at Port Erin 

 all the year round. The numbers begin to get progres- 

 sively larger in April, May and June, to a maximum in 

 July, after which they decrease irregularly through 

 August and September. The greatest haul (54,350 on 

 July 31st) is more than twice as large as the top haul 

 of 1910. 



Oithona simiUs. — The commonest Copepod in Port 

 Erin Bay throughout the year is again Oithona similis. 

 The greatest haul is 225,450 on July 18th, a very large 

 number for a Copepod, in our standard hauls, and nearly 

 twice as much as the largest ( 126,700 at Station I on 

 August 20th) of the previous year. In general, the 

 record is the same as before. 



Temora longicornis. — This is a summer form, and 

 this year it was only abundant in June and July. It has 

 a remarkably symmetrical distribution, forming a simple 

 normal curve, rising from an average of 1 per haul in 

 January, having the maximum in summer, and sinking 

 to 2 per haul in December. The average for June is 

 4,675 per haul and for July 4,706, and the two largest 



