NATURAL HISTORY STUDIES 



To keep a famous inland fish-pond from becoming 

 barren, recourse was had to an interesting device. 

 Some boxes of mud and manure were placed at the 

 sides, yet so that none of the manure got into 

 the water. Bacteria, the microscopic minions 

 of all putrefaction, began to work in the mud and 

 manure, making food for minute, but not quite so 

 minute, animalcules called Infusorians, which mul- 

 tiply so rapidly that there may be a million from one 

 in a week's time. A living cataract of these Infu- 

 sorians overflowed from box to pond, and " water- 

 fleas," which are really tiny Crustaceans about the 

 size of pins' heads, gathered at the foot of the fall, 

 devoured the animalcules, and multiplied exceed- 

 ingly. But the water-fleas are eaten by fishes, so 

 that the fishes were kept in good cheer. As fish- 

 flesh is said to be good for the brain, we have traced 

 the links of a chain connecting mud and clear 

 thinking ! What was in the mud became part and 

 parcel of the Infusorians, which became part of the 

 Crustaceans, which became part of the fishes, which 

 became part of the man. And so the world goes 

 round. 



It has been shown that the more sunshine there is 

 in the spring-time, the more mackerel there is at 

 Billingsgate market. The mackerel feed daintily on 

 water-fleas called Copepods in the sea, and these 

 feed on microscopic plants and animals (Diatoms 

 and Infusorians) which form what we might call 

 the " stock " of the " sea-soup." But the produc- 

 tion of these minute creatures, of which there may 

 be millions in a few gallons, depends partly on the 



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