48 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
These diatoms began in March, when the alkalinity was 
low, that is to say, when the carbon dioxide in the water is 
great in amount, and their vernal maximum coincides with 
the top of the alkalinity curve, that is to say when the carbon 
dioxide is relatively small in amount. The carbon that was 
present as that gas is not lost, but it is now present in another 
form, as parts of the living bodies of the diatoms, and had 
not the inorganic carbon been available as food these abundant 
swarms of living things could not have been produced. 
After the vernal maximum the diatoms begin to die off, 
and disappear for a time, their place bemg taken as the 
dominant organisms of the sea-water, for a period in early 
summer, by the minute shrimp-hke animals known as Copepoda. 
I do not propose to follow these changes in the plankton 
any further throughout the year, but if the so-called “ practical 
man” were to ask me whether all these changes in the sea, 
chemical and vital, have any relation to man and his industries, 
I would answer, “‘ Only this—that the whole life and develop- 
ment of fishes in the sea seems to depend upon them ”—as I 
shall show you presently. But, first, let me say that, personally, 
I do not attach much importance to demonstrating the 
practical utility of a scientific discovery. I am content to 
leave it to demonstrate itself, knowing well, that if it is true 
it will sooner or later be justified in the mind of even the most 
utilitarian of men. The history of science bristles with 
examples of discoveries in pure science which at first seemed to 
have no obvious relation to man or his material wants, and 
which have since formed the foundation of, it may be, a 
chemical industry or an electrical enterprise, or some develop- 
ment of radio-activity. No better mstance could be taken. 
than the change in attitude of the man-in-the-street towards 
the study of mosquitos and flies. 
A few years ago, you will agree with me, the Entomologist 
was looked upon with a benevolent smile as an amiable old 
