352 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



plankton is carried up this channel, the proximity of 

 numerous small islands and rocks, and of the long coast 

 lines of Mull, Islay and Jura, is bound to supply some 

 neritic forms, and these may be carried unusually far 

 out to sea by the strong tidal currents that prevail here 

 in the neighbourhood of the Coryvrechan whirlpool. 



North End of Mull. 



This year we have had three vertical hauls from 

 practically the same spot, off Ardmore at the north 

 end of the Sound of Mull, one on August 5th from 

 109 fathoms, and two on August 22nd from 78 and 100 

 fathoms. All three were of very much the same type, in 

 each case mainly zoo-plankton added to a certain amount 

 of phyto-plankton, from four to six species of Diatoms, 

 represented by numbers of some hundred to about forty 

 thousand individuals each, and the general nature of the 

 majority of the speciesi in each case is oceanic. All this 

 agrees very closely with the haul taken on July 11th, 

 1911, from 105 fathoms, but differs markedly from the 

 phyto-planktonic and mainly neritic hauls obtained at 

 that same spot in July, 1909 and 1910. The evidence 

 seems to point to the conclusion that earlier in the 

 season the water in that region may be occupied by a 

 neritic phyto-plankton, which becomes replaced later on 

 by an invasion of zoo-plankton from outside. If that 

 explanation is correct, then it would appear that the 

 phyto-plankton lingered on to a later date in 1909 and 

 1910, or that the oceanic invasion was greater in 1911 

 and 1912. As distinctly oceanic forms which made their 

 appearance in the Ardmore vertical hauls this year we 

 may note the Copepod Metridia lucens (in every haul) 

 and the Siphonophore Cwpulita sarsi (see below). 



