WHITEFISH OF THE LAKE OF GENEVA 



sustenance they supply, they too, must live, and find 

 around them, in the water in which they live, flesh 

 upon which to feed. The cycle of nutrition in the 

 lake does not stop at the tiny crustaceans; it goes on 

 until it comes to the creatures, even more minute, 

 upon which the water-fleas and their kind feed. We 

 discovered in the stomachs of the whitefish what was 

 left of their meals : now, in the stomachs of the little 

 crustaceans, we see, under the microscope, the remains 

 of the creatures upon which they have fed. These 

 are protophytes and protozoans, unicellular vegetables 

 and animals, invisible to the naked eye, but there none 

 the less, in even greater numbers than those for whom 

 they form the means of existence. 



I take up the bottle which I filled when I threw out 

 my plankton net. I bring it up to the level of my 

 eyes and look through it against the light. There are 

 the tiny crustaceans, swimming about in fits and starts, 

 bolting about in all directions, but I cannot see any- 

 thing else. The naked eye can discern nothing more. 

 But if I go back to the laboratory, take a single drop 

 of that water, and put it on a glass slide beneath a 

 microscope of high power, I see great numbers of 

 unicellular creatures whose size can only be measured 

 in fractions of a millimetre. Nearly all of them are 

 too small to be recognized by our sight; and under 

 natural conditions we cannot distinguish them at all. 

 Most of them are transparent or only slightly coloured, 

 and this adds to our difficulty in seeing them: yet 

 they exist, living, swarming, and people with their 

 myriads of minute individuals the whole water from 

 the surface to the bottom. 



Tourists go into rhapsodies over the beauties of the 

 lake. From their boat, as it moves smoothly over the 

 calm waters, they admire the sky, the mountains on 

 the horizon and, more than anything else, the water 

 itself, that wonderful deep -blue water whose purity 

 and limpidity they find so remarkable. But such 

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