154 THE HAUNTS OF LIFE 



of Gihon, at the Jaffa Gate, and put it in a pill- 

 box. It lay dry for forty years, but, when 

 some of the dry dust was then put into a saucer 

 full of water, it gave rise after a short time to 

 some lively water-fleas. Their resting-eggs had 

 retained their vitality for longer than an aver- 

 age human lifetime. This explains why pools, 

 which have been dry for several years, are 

 found teeming with little creatures soon after 

 they have been once more filled with water. 

 The power of lying low in the mud also helps 

 us to understand what we considered already, 

 that similar fresh-water animals often occur 

 in widely separated basins. For mud may be 

 transported for long distances in various ways, 

 e.g. on the coats of cattle, and on the feet of 

 birds. When the caked mud is dissolved off 

 in the water, the minute animals may become 

 lively again, or sometimes it seems to be their 

 well-protected eggs that have survived. 



In tropical Africa there is a strange fish 

 which has lungs as well as gills. It is known 

 as the " mud-fish " because, when the water of 

 the lake in which it lives gets very low, it bur- 

 rows down into the mud, and works itself 

 round and round until it has formed a com- 

 plete mud-casing round its body. This dries 



