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MARINE BIOLOGICAL STATION AT PORT ERIN. 47 
the Isle of Man, in which case the 300,000 tons would be 
distributed through the zone of water extending to about one 
mile out from the shore, and down to an average depth at 
that distance of, say, ten fathoms. Now, all of these organisms 
have obtained their carbon from the carbon dioxide present in 
the sea-water in spring, and it is absolutely certain that in the 
absence of this abundant supply of available carbon-food, 
the millions and millions of organisms in question could never 
have existed. This explains the connection which I 
mentioned above between the periodic chemical changes in 
alkalinity, due to variations in the carbon dioxide present, and 
_ the periodic changes in the living contents of sea-water. 
In early spring there is a great awakening in the 
oceans comparable with the growing of the grass and the 
budding of the trees on land. This increase and growth of 
livmg things starts in our sea here about March, when the 
temperature of the water (which lags behind that of the air) 
is about at its lowest. So it is evident that temperature has 
nothing to do with this germination, although it is quite possible 
that the marked increase of sunlight has. These early spring 
organisms, the diatoms, constituting the phytoplankton, as 
it is called because of its vegetable nature, increases with 
astonishing rapidity during March and April, until it reaches 
what we know as the vernal maximum, when these diatoms 
are so abundant all through the water of the Inish Sea, that 
a short haul of a fine silk net towed along the surface will 
catch anything from one up to a couple of hundred millions 
of individuals. Moore’s figures for the turn-over of carbon in 
spring indicate that there is probably a production each 
season of about two tons of dry organic matter per acre, 
corresponding to at least ten tons of moist vegetation— 
which shows that we may still be very far from getting from 
our seas anything like the amount of possible food-matters 
that are produced. 
