24 The Life Story of the Fish 



have known it, but it is only within the last fifty years that 

 they have known how much the scale might reveal about its 

 owner. This was partly because until Leeuwenhoek, the early 

 lens-maker, began his painstaking grinding of glass in Hol- 

 land in the late seventeenth century, there was no way to 

 see what the scale had to tell. But the fact that it was not 

 until two hundred years after Leeuwenhoek that his discov- 

 ery began to be applied to the reading of scales indicates 

 that the real reason was that no one cared. As long as man 

 was so widely scattered over the earth that he could get fish 

 whenever he wanted, either for food or for sport, it wasn't 

 necessary for him to cultivate them. But then man began to 

 invent machines. Machines had a threefold effect upon his 

 relation with fish. In the first place, machines brought about, 

 indirectly, a great increase in human population, and there- 

 fore a great increase in the number of potential fish-eaters 

 and of potential fishermen. In the second place, they pro- 

 vided means whereby fish could be brought to fish-eaters 

 far from the home of the fish without becoming unappetiz- 

 ing. And in the third place, they made it possible for sports- 

 men to transport themselves with the greatest of ease from 

 cities, inland prairies, and other places where fish do not live 

 to streams and oceans where they do live. 



When the resulting demand began to outrun the supply, 

 man realized that he was in danger of destroying one of his 

 most valuable resources. He began to study fish from the 

 practical point of view as well as the scientific. In other 

 words, he began to study the animal as a crop to be har- 

 vested, as well as a specimen to be classified and dissected. 

 He brought the microscope to bear on the subject, and found 

 that, at least in certain of the species in which he was par- 

 ticularly interested, the scales contained a record of the fish's 

 life. 



When the fish first comes out of its ^gg^ it has no scales. 



