MARINE BIOLOGICAL STATION AT PORT ERIN. 49 
gentleman, perhaps harmless, but certainly for practical 
purposes the most useless of cranks. And yet it is the results 
of these men’s work—of their patient investigation of the 
life-histories and habits of the disease-bearing flies, as applied 
by the United States Sanitary Service, that have rendered 
possible that great engineering feat, the completion of the 
Panama Canal. It was not any engimeering difficulties that 
prevented the French, quarter of a century ago, under De 
_ Lesseps, from cutting the isthmus, but merely that sanitary 
science, based upon the work of field-naturalists and micro- 
_ scopists, was not then far enough advanced to permit men to 
put up a successful fight against malaria and yellow fever. 
However, I have no objection to pomt out a utilitarian 
- connection where one can be seen to exist. Practically all our 
food-fishes in the sea, except the herring, produce their eggs 
in winter or early spring. They are hatching out in_ vast 
quantities during the time that the alkalinity is rapidly 
increasing and the phytoplankton of diatoms is daily growing 
in amount. | 
Now, soon after the little larval fishes have been hatched 
from the eggs, diatoms are exactly what they require as food. 
So we may put the connection this way—the increasing 
alkalinity in spring is a measure of the rate at which the 
_ diatoms are converting the inorganic carbon of carbon dioxide 
into the organic carbon of their own living bodies suitable 
to be the food necessary for the young cod, haddock and 
_ whiting, and plaice, soles and flounders then being hatched out. 
A little later on, in early summer, when the vernal maxi- 
mum of phytoplankton is over, and the diatoms have been 
replaced by copepoda, we find the same little fishes, now 
grown larger and stronger, feeding not on the vegetable food 
_ of their early babyhood, but upon the animal food in the form 
_ of copepoda, by which they are surrounded. 
I excepted herring just now from the fishes mentioned, 
