748 



SCIENCE 



[N. S. Vol. XXX. No. 778 



ter a million times as big as the sun. The 

 destruction that keeps such a rate of re- 

 production in check must be equally as- 

 tonishing. It is claimed that the Valdivia 

 results, and observations made since show 

 that the most abundant plankton is where 

 the surface water is mixed with deeper 

 layers by rising currents. Nathansohn, 

 while finding that the hour of the day has 

 no effect on his results, considers that the 

 development of the phyto-plankton corre- 

 sponds closely with evidence of vertical cir- 

 culation. Like some other workers, he em- 

 phasizes the necessity of continuous inten- 

 sive work in one locality ; such work might 

 well be carried on both at some point on 

 your great lakes and also on your Atlantic 

 coast. The Challenger and other great ex- 

 ploring expeditions forty years ago opened 

 up problems of oceanography, but such 

 work from vessels passing rapidly from 

 place to place could not solve our present 

 problems— the future lies with the natural- 

 ists at biological stations working continu- 

 ously in the same locality the year round. 

 The problems are most complex, and may 

 vary in different localities— for example, 

 there seem to be two kinds of diatom max- 

 ima found by Nathansohn in the Mediter- 

 ranean, one of Chcetoceros due to the afflux 

 of water from the coast, and one of Rhizo- 

 solenia calcaravis, due to a vertical circula- 

 tion bringing up deeper layers of water. 

 As a local example of the importance of 

 the diatoms in the plankton to man, let me 

 remind you that they form the main food 

 of your very estimable American clam. 

 The figures I now show, and some of the 

 examples I am taking, are from the excel- 

 lent work done on your own coasts in con- 

 nection with fisheries and plankton by 

 Professor Edward Prince and Professor 

 Ramsay "Wright and their fellow workers 

 at the Canadian biological station, on your 

 eastern seaboard. 



The same principles and series of facts 

 could be illustrated from the inland waters. 

 Your great lakes periodically show plank- 

 ton maxima, which must be of vast impor- 

 tance 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 to further reduce this valuable source 

 of food ! Quoting from your neighbors to 

 the south, we find that the Illinois fisheries 

 yield at the rate of a pound a day through- 

 out 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 

 pounds in a year; and all scientific men 

 who have considered fishery questions wiU 

 note with approval that all your fishing 

 operations are now carried on under regula- 

 tions 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 meth- 

 ods 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 uncultivated 

 water may equal that yielded by cultivated 

 land. When aquiculture is as scientific as 



