THE FRESH WATERS 153 



within the mosquito and multiplies there ; when 

 the mosquito bites another man it infects him 

 with the malaria germs of which it is the car- 

 rier. Pouring a little paraffin on stagnant pools 

 so alters the nature of the surface film that the 

 larval mosquito, which lives in the water, can 

 no longer hold on to it with its breathing-tube, 

 and dies for lack of oxygen. Moreover, as there 

 are little fishes that greedily devour the larvae 

 of mosquitoes, and are very useful in water- 

 tanks where the use of paraffin is impossible, 

 we may actually link little fishes to the decline 

 of Greece. " Ye gods and little fishes ! " 



THE DANGER OF DROUGHT 



Life in fresh waters has its peculiar difficul- 

 ties, and the three greatest are: DROUGHT, 

 FROST, and FLOODS. Especially in warm coun- 

 tries is there great risk of the pool drying up. 

 Little wonder then that many fresh-water ani- 

 mals have learned to lie low in a state of latent 

 life. Some small crustaceans have been known 

 to lie for forty years in dried mud, without 

 losing the power of actively living when the 

 mud was moistened again. A naturalist visit- '' 

 ing Jerusalem took a little mud from the pool 



