366 ZOOLOGY. 



3. By studying the habits of the fishes and by regulation of 

 the time, place and manner of catching. 



382. Supplementary Exercises for the Library. 



1. Make a report concerning the principal food fishes used by the 

 people of the United States : their habits and geographical range, the mode 

 of their capture and putting on the market. 



2. Make a study of the methods of capturing fish from primitive time 

 to the present and show how the methods have been adapted to the habits 

 of the fish. 



3. A study of the history and work of the United States Fish Com- 

 mission as shown in the annual reports and bulletins. Its economic side. 

 Its scientific side. 



383. Reproduction and Development. The sexes are 

 separate. The sexual elements are produced in great numbers. 

 The ova (spawn) are usually deposited in the water, in shal- 

 lows on the open bottom, under rocks, or in places specially pro- 

 vided for them by the parents. The sperm ( milt} is poured over 

 these by the male, and the fertilization and later development 

 take place in the water with little or no care on the part of the 

 parents. Great loss of life occurs among the young from the 

 voracious habits of other species and sometimes of the parents 

 themselves. It is not difficult to believe that the enormous 

 number of eggs produced by the female is an adaptation to 

 meet this risk of mortality among the young. In some cases 

 (most sharks and a few bony-fishes) the eggs are fertilized 

 and the young hatched within the body of the mother. Only 

 a few young are produced in such forms. 



The eggs of fishes are usually well supplied with yolk, seg- 



FIG. 182. 



FIG. 182. The Smelt (Osmerus dentax). Bull. U. S. Fish Commission. 



