30 PEOCEEDINGS OP THE 



Sagitta is present throughout the year ; it is most abundant in 

 August, and the minimum occurs in winter (January to March). 



As showing the difference produced by a lai'ger net of wider 

 mesh, we find that during April, when the hauls with the ordinary 

 tow-nets were giving units and tens, those taken at the same 

 time with the shear-net ran into hundreds, as follows : — 360, 

 123, 286, 310, 200, 200, 400, 400, 300, 800. The fact, however, 

 that the weighted tow-net, not invariably, but usually, took a much 

 larger number than the similar surface-nets, shows that Sagitta is 

 usually more abundant in a zone of water below the surface, 

 extending down to 10 fathoms, and that consequently the much 

 greater numbers obtained by the shear-net may be due not wholly 

 to the size of the net and mesh but in part to the depth at 

 which it was worked. 



The Nauplius and Cypris stages of Balanus form an interesting 

 study. The adult Barnacles are present in enormous abundance 

 on the rocks of Bradda Head, and they reproduce in winter, at 

 the beginning of the year. The Nauplii first appeared in 1907 

 in the bay gatherings on February 22nd, and increased with ups 

 and downs to their maximum on April 15th, and then decreased 

 until their disappearance on April 26th. None were taken at any 

 other time of the year. The " Cypris " stage follows on after the 

 Nauplius. It is first taken in the bay on April 6th, rises to its 

 maximum on the same day with the Nauplii, and was last caught 

 on May 24th. Throughout, the " Cypris " curve keeps below that 

 of the Nauplius, the maxima being 1,740 and 10,500 respective!}'. 

 Probably the difference between the two curves represents tlie 

 death-rate of the Balani during the Nauplius stage. 



The two large Copepoda Calanns helgola adieus (Claus) and Ano- 

 malocera paitersoni. Temp., are both regarded as " oceanic " species, 

 and are both present in fair abiindanee in the Irish Sea. They 

 are two of the most conspicuous objects in our plankton gatherings, 

 and can readily be picked out with the eye and counted. 



Calanus was present in our gatherings in 1907 during every 

 month of the year from January 8th to December 30th. It was 

 represented on nearly every occasion when hauls were taken, and 

 in some cases when absent from one net it was taken in another 

 gathering made on the same day, showing that the apparent 

 absence was due either to irregular distribution or to some imper- 

 fection in the sampling of the sea. When, then, we find that a 

 species like this is not recorded from a particular haul at a time 

 of year when gatherings are being taken once a week only, one is 

 inclined to suspect from the appearance of the records at other times 

 when the observations were more frequent, that if another haul 

 had been taken that day or on an adjoining day the species would 

 have been represented. 



Anomalocera, on the other hand, first appears in our records 

 on March 29th, and then only in the form of metanauplii (100, 

 170, and 30 in surface hauls off the Calf Island). It continues 

 to be represented, in small numbers, by both adults and young, 

 throughout August and September, and finally on November 8th. 



