MARINE BIOLOGICAL STATION AT PORT ERIN. 49 



Nathansohn in the Mediterranean, one of Chaetoceros 

 due to the afflux of water from the coast, and one of 

 Rhizosolenia calcar-avis, due to a vertical circulation 

 bringing up deeper layers of water. 



The same principles and series of facts could be 

 illustrated from the inland waters. Lakes periodically 

 show Plankton maxima, which must be of vast importance 

 in nourishing animals, and eventually the fishes used by 

 man. 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 now the 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. It is to be hoped that 

 nothing will be done further to reduce this valuable 

 source of food. It is said 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. 

 The Canadian whitefish' alone has yielded, I see, in 

 recent years over 5,000,000 lbs. in a year, and all 

 scientific men who have considered fishery questions will 

 note with approval that all the fishing operations are now 

 carried on under the regulations of the Dominion 

 Government, and that fish hatcheries have been established 

 on several of the 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. It has been shown in European 

 seas that the mass of living food matters produced from the 

 uncultivated water may equal that yielded by cultivated 

 land. When aquiculture is as scientific as agriculture the 



