A MOUNTAIN STREAM 163 



crowded life. There are freshwater Snails, for instance, 

 like Lymnaeus, with its shell in a spiral, and Ancylus, 

 like a tiny limpet. There are freshwater Crustaceans, 

 like Gammarus pulex, one of the scavengers of the, 

 bed of the stream. There are insect larvae of many 

 different kinds, young- May Flies, young Stone Flies, 

 young Caddis Flies in their jackets of stick fragments 

 and tiny pebbles. There are several different kinds of 

 Leeches, one of which, called Clepsine, carries its 

 young ones about with it attached to the ventral 

 surface one of the humblest illustrations of parental 

 care in the animal kingdom. There are small flat 

 Worms called Planarians, gliding along mysteriously 

 like tiny pieces of leaf; they are moving by means of 

 microscopic lashes or cilia that cover the surface of 

 their filmlike body. We have noticed that some of 

 these are found high up the stream, halfway up the 

 mountain. There are freshwater sponges on the stones 

 and bank posts of the river, but we never found them 

 in the lesser stream. But besides these visible creatures 

 and we have only mentioned a few samples there 

 are scores and scores too small for the naked eye 

 to see. 



Towards the end of May the Elvers or young Eels 

 come up our river, but the date for different rivers 

 varies according to the distance of the mouth from the 

 Atlantic. These Elvers that come up in thousands, 

 hugging the bank of the river and hiding under stones 

 when the sun sets, are already about two years old, 

 their earlier youth being spent in the open waters of 

 the ocean. We must not tell the story now, but the 

 Elvers explore the tributaries of the river, and those 

 that are successful in finding good hunting-ground 



