FRESH WATER 



197 



enters the water freely and fishes among the stones for small 

 animals, now holding on with its toes, and now beating its wings. 

 The large oval nest of moss, grass, or leaves is to be looked for 

 in a hole in the bank or about a bridge or behind a waterfall, and 

 it may be noted that the eggs, like many but by no means all 

 well-hidden or inaccessible eggs, 

 are pure white. 



Freshwater Fishes. In some 

 of our rivers there are still 

 lamperns (Petromyzon fluviatilis\ 

 but one is more likely to find 

 the young of the sea lamprey 

 (Petromyzon marinus\ often 

 called " niners," which are in- 

 teresting creatures to study. 

 Primitive vertebrates they are 

 rather than fishes. Some refer- 

 ence has been made in another 

 part of this book to the salmon 

 and the eel, and at the proper 

 season we should peer down from 

 the bridge to see the female 

 salmon dropping her eggs each 

 the size of a small pea into the 

 furrow which she has ploughed 

 in the gravelly bed, or watch by 

 the side of the stream to see 

 the marvellous yearly journey of FIG. 114. Three-spined stickleback (Gas- 



the " elvers " which make their trosteus aculeatus], and nest fastened to 



way up stream with so much ^ter weeds, 

 persistence. In some parts of the country children are familiar 

 with the dramatic sight of the salmon going up the rapids 

 and leaping a waterfall, and in the same or other rivers the 

 spectacle of large numbers of big full-grown eels going down 

 stream to the sea is not uncommon. To illustrate the studies 

 which have been suggested in the chapter on Fishes, we can find 

 abundant material in the fresh waters with their pike, perch, 

 trout, minnow, roach, loach, carp, miller's thumb, and stickleback. 



