332 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



(but not an excessive amount), are typical of what may 

 be expected in such cases. 



An early salinity maximum of somewhat over 34'4 

 in December succeeded by a magnificent summer like 

 that of 1911 in the following year seems to result from 

 the third type of circulation. And lastly, when the 

 oceanic circulation is of type (d) the Gulf Stream Drift 

 water is sufficiently cold to be heavier than the Salter 

 water of Mediterranean origin which normally flows 

 northwards below it. The Salter water consequently 

 rises to the surface and enters the English Channel and 

 Irish Sea, leading to a salinity maximum of about 34'6 

 on the line Holyhead — Calf of Man in February. In 

 spite of the high salinities in the Irish Sea the conditions 

 in the Atlantic are probably more unfavourable 

 from the meteorological point of view than even those 

 corresponding to type (6). The type of summer 

 experienced in 1912 with an excessive rainfall- — often 

 of a thundery character — appears in fact to be associated 

 with hydrographic conditions of this nature. 



It may be mentioned that a number of southern 

 forms not usually found in the plankton of the Irish Sea 

 were noticed during 1912. Large numbers of the 

 " Portuguese man-of-war " (Caravella sp.) were taken 

 in the English Channel*, and I even found one _ on the 

 shore of Carnarvonshire, near Criccieth, on April 5th. 

 The presence of such southern forms, though not proving 

 the entry of Mediterranean water into our area, is, 

 nevertheless, quite intelligible on such a supposition. 



Our observations for January, February and March, 

 1913, again show very high salinities, as can be seen 

 from the following figures for Stations V, VI and VII : — 

 * Also in Feb. (Nature, Feb. 27) and Mar., 1913. 



