LIXNEA.K SOCIETr Or LOXDON. 3 1 



The distribution ol Microcalanus pusilhis, Gr. O. Sars, throughout 

 the year is interesting. It appears for the first time in our records 

 late in August, and remains fairly constantly present but never very 

 abundant throughout the autumn until January, when it disappears. 

 During the first few weeks it is only in the offshore hauls, 

 appearing first out in mid-channel on August 24th in the Hensen 

 and Nansen nets that were let down to 60 fathoms and hauled up 

 vertically. As specimens were present in all the nets that were 

 closed when they had been pulled up to 45 fathoms, and were 

 not present in the surface and other nets used above this level, 

 it is evident that this Copepod was on its first appearance only in 

 the deep water in mid-channel. It was encountered next on 

 August 26th, in the weighted net hauled at 10 fathoms, on the inner 

 edge of the Train bank, some eight miles off land. On August 31st 

 it made its appearance at Station I in the Hensen and Nansen 

 nets hauled up from 24 fathoms, and in the weighted net from 

 10 fathoms — the latter having 350 specimens. It was also present 

 on September 2nd and 3rd, under the same circumstances. On 

 September 4th we again fouud it in n)id-channel in the vertical 

 nets which had been down to 60 fathoms ; it was still not present 

 in the surface-nets nor in the inshore waters. 



On September 6th, Microcalanus appeared for the first time 

 inshore, at Station IV, off the Calf Island, but only in the Hensen 

 and Nansen nets which had been closed at 8 and 15 fathoms 

 respectively ; it was not present in the surface hauls taken at the 

 same time. It was next met with on September 1 1th, ab Station Y, 

 south of Calf Sound, inside the Wart Bank, when 100 specimens 

 were taken in each of the two surface-nets, 150 in the weighted 

 net at 10 fathoms, and 5, 5, 5, 3, in the four vertical nets (2 

 Hensen and 2 ]^ansen) hauled from 20 up to 10 fathoms. It had 

 evidently become distributed by this time all through the water 

 around the Calf Island. The following day, the species w^as 

 present in nearly all the numerous nets worked at various depths 

 down to 60 fathoms in mid-channel ; and it then reached its 

 climax in numbers, 2000 in the net at 10 fathoms and 2500 in an 

 open tow-net attached to the shear-net at 20 fathoms. Finally, 

 on September 21st Microcalanus turned up for the first time in 

 the surface gatherings taken across Port Erin Bay. It was present 

 in these bay gatherings on October 1st (35) and 24th (100), 

 November 8th (100), December 20th (80) and 23rd (50), and 

 finally January 8th (50 specimens). 



This record looks like the immigration of an oceanic species in 

 summer up the deep water of the mid-channel between the Isle of 

 Man and Ireland, and then its gradual spread in late autumn into 

 the shallower inshore waters and fiiiall}' to the surface of the bay, 

 where it remained throughout the winter. 



Centropages hamatus (Lilljeborg) occurs in the Irish Sea all the 

 year round. It is on our records for 1907 in every month, and is 

 practically continuously present from January 8th to December 

 30th. The numbers are low at the beginniug of the year, but 

 reach 600 in one haul of the surface-net by April 9th, and 1300 



