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. Pouringa 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 larve 
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, 
FRostT, and FLoops. 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 
