350 



A COURSE ON ZOOLOGY. 



what surroundings 

 the eggs are laid, 

 and what nourish- 

 ment must be fur- 

 nished the young 

 fish or spawn. 



Some species, 

 such as the trout 

 and salmon, de- 

 posit their eggs in 

 little cavities in 

 sand or gravel, or 

 in the interstices 

 of rocks; others, 

 such as the perch, 



g carp, and roach, 



attach the eggs to 

 aquatic plants or 

 stones by the aid 

 of a viscid, glue- 

 like matter. These 

 conditions being 

 known, it is easy 

 to establish an ar- 

 tificial hatchery. 

 For the perch 

 tribe a frame of 

 wood, supporting 

 a net - work of 

 branches and a- 

 quatic plants, may 

 be sunk in the 

 water by means of 



