THE FRESH WATERS 153 



mosquito and multiplies there ; when the 

 mosquito bites another man it infects him with 

 the malaria germs of which it is the carrier. 

 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 difficulties, 

 and the three greatest are : DROUGHT, pROST,and 

 FLOODS. Especially in warm countries is there 

 great risk of the pool drying up. Little wonder 

 then that many fresh-water animals 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 visiting Jerusalem took a 

 little mud from the pool of Gihon, at the Jaffa 



