MARINE BIOLOGICAL STATION AT PORT ERIN. 33 
from the same localities in different years, two con- 
clusions become evident : — 
1. That localities, in some cases not very far apart, 
differ very considerably in the nature of their plankton 
at the same time of year. 
2. That there is a constancy year after year in the 
nature of the plankton at some localities. 
A few examples will make this clear :—- 
1. In the northern area (north of Oban) the hauls 
taken in Loch Hourn and Loch Nevis, off the Sound of 
Sleat, are on all occasions very different from those taken 
off Ardmore in Mull, and from those taken off the Island 
of Canna; also those taken in the Lynn of Morven at one 
end of the Sound of Mull differ from those taken between 
Mull and Ardnamurchan at the opposite end. Again, 
in the southern area (the Clyde sea-area) the hauls from 
off Skate Island, in the entrance to Loch Fyne, differ 
markedly from those taken further south in the Sound 
of Bute and the Firth of Clyde off Arran. 
2. The Loch Fyne vertical hauls are always 
characterised by the abundance of large Copepoda; the 
hauls off Canna and elsewhere in the sea of the Hebrides 
by the prevalence of Diatoms; those in the Firth of 
Lorn by a fine Zoo-plankton, and those round Raasay, 
north-east of Skye, by a much coarser Zoo-plankton. 
Thus we have evidence that off the north-west coast 
of Scotland, at one time of year (July) in several 
successive seasons, the plankton as sampled by vertical 
hauls was of different types (Zoo- and Phyto-plankton) 
in different localities, but preserved a constant character 
in each. 
Now in the Irish Sea, around the Isle of Man, when 
the plankton of the whole year is considered, it is clear 
that neighbouring localities do not present widely 
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