148 THE BOOK OF NATURE STUDY 



the " marbled angler " from the Sargassum weed). They are not 

 always absent when they seem to be absent, and it is an in- 

 structive exercise to mount a small piece of the skin of the 

 slippery eel, showing its minute but perfectly distinct scales. 

 Even this demonstration alone would justify a school lesson 

 on scales. 



THIRD STUDY: THE LIFE-HISTORIES OF FISHES 



The study of life-histories is always fascinating, and those 

 of fishes are among the most interesting. It must be remem- 

 bered, however, that Nature Study is a definitely observational 

 study of a particular environment, and that the teacher must 

 not allow himself to be led too often along the pleasant path of 

 telling " fairy-tales of science." We shall refer here to the life- 

 history of the salmon and of the eel, two very familiar fishes. 



Life-History of Salmon. Some of the children live by the sides 

 of a salmon-river ; they have seen the salmon leaping ; they 

 may have seen the female fish laying her eggs ; they have seen 

 the salmon caught in different ways. If Nature Study means 

 anything in such a place it means inquiry into the habits and life- 

 history of the salmon, and from this we are not to be deterred 

 though many of the problems that surround the salmon are still 

 unsolved. 



The eggs are laid in the winter months in the sandy and 

 gravelly bed of the stream by the female salmon, and fertilised 

 there by the male salmon. The eggs have many enemies, and 

 many perish. Those that survive develop very slowly, taking 

 three to four months to hatch. The eggs can be readily hatched 

 in a little tub with sand at the bottom, if a slow flow of water is 

 secured. 



At first the young ones are very sluggish and lie among the 

 stones, living on then: legacy of yolk, which may last for fifty 

 days. As the yolk becomes exhausted they become more active, 

 and about eight weeks after hatching (i.e. in spring) the fry are 

 about i inch long. They now grow quickly, feeding on minute 

 creatures in the water, and by the end of a year they are some- 

 what trout-like "parr" about 4 inches long. 



