SEA-FISHERIES LABORATORY. 321 



follows : — " The seas on the west coast of Scotland are on 

 the border line of the last two kinds of water, and may be 

 regarded as primarily an area of Coastal water which is, 

 however, periodically invaded to a greater or less extent by 

 bodies of warmer and Salter Atlantic water carrying in 

 oceanic plankton. The variations which we find in 

 different years in the nature and amount of the plankton, 

 at the same localities, no doubt depend upon the volume 

 and period of such invasions. They may depend also upon 

 other factors, such as the weather (temperature, sunshine, 

 rainfall, wind, &c.) at the time, and previously." 



To this we may now add that the presence of 

 Doliolum last summer and not this, and of Limacina this 

 summer and not last, is a good example of such variations 

 in the oceanic invasions of zoo-plankton. The two 

 summers were very different in character; 1912 was cold, 

 wet and stormy, while 1913 gave us for the most part 

 fine weather and calm seas; but although the two fine 

 Augusts of 1911 and 1913 showed quantities of Limacina 

 and the intermediate bad summer showed none, still we 

 hesitate to do more than record the facts : there may be 

 no connection between the weather and such variations in 

 the plankton as we have observed. 



We may remark, finally, that both (1) the lingering 

 of the phyto-plankton in more northerly waters, with 

 occasional very large swarms of diatoms, and (2) the 

 oceanic invasions from the Atlantic constitute a marked 

 difference between a collection of summer plankton from 

 the West Coast of Scotland, North of the Mull of Cantyre, 

 and a collection made at the same time from the more 

 enclosed waters of the Irish Sea. 



