746 EVENING DISCOURSES. 
nection with fisheries and Plankton by Professor Edward Prince and 
Professor Ramsay Wright and their fellow-workers at the Canadian bio- 
logical station on your eastern sea-board. 
The same principles and series of facts could be illustrated from the 
inland waters. Your great lakes periodically show Plankton maxima, 
which must be of vast importance in nourishing animals and eventually 
the fishes used by man. Your geologists have shown that Manitoba was in 
post-glacial times occupied by the vast lake Agassiz, with an estimated area 
of 110,000 square miles; and while the sediments of the extinct lake form — 
your celebrated wheat-fields, supplying food to the nations, the shrunken 
remains of the water still yield, it is said, the greatest fresh-water fisheries 
in the world. See to it that nothing is done further to reduce this 
valuable source of food! Quoting from your neighbours to the South, we 
find that the Illinois fisheries yield at the rate of a pound a day throughout 
the year of cheap and desirable food to about 80,000 people—equivalent to 
one meal of fish a day for a quarter of a million people. 
Your excellent ‘ whitefish ’ alone has yielded, I see, in recent years over 
5,000,000 lb. in a year; and all scientific men who have considered fishery 
questions will note with approval that all your fishing operations are now 
carried on under regulations of the Dominion Government, and that fish 
hatcheries have been established on several of your great lakes, which will, 
along with the necessary restrictions, form, it may be hoped, an effective 
safeguard against depletion. Much still remains to be done, however, in 
the way of detailed investigation and scientific exploitation. The German 
Institutes for Pond-culture show what can be done by scientific methods to 
increase the supply of food-fishes from fresh waters. It has been shown in 
European seas that the mass of living food matters produced from the un- 
cultivated water may equal that yielded by cultivated land. When aqui- 
culture is as scientific as agriculture your regulated and cultivated waters, 
both inland and marine, may. prove to be more productive even than the 
great wheat-lands of Manitoba. 
Inland waters may be put to many uses: sometimes they are utilised as 
sewage outlets for great cities, sometimes they are converted into com- 
mercial highways, or they may become restricted because of the reclamation 
of fertile bottom lands. All these may be good and necessary developments, 
or any one of them may be obviously best under the circumstances ; but, in 
promoting any such schemes, due regard should always be paid to the im- 
portance and promise of natural waters as a perpetual source of cheap and 
healthful food for the people of the country. 
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