TBIE REQUIRED FOR DEVELOPMENT. 101 



the young fry soon begin to pine if the ther- 

 mometer marks many degrees over 55°/''' 



The proper temperature of the water both 

 in and out of doors ought to range from 40° 

 to 45°. Mr. Ponder's observations tell him 

 that at this temperature it requires thirt^- 

 five days for the eyes to appear (^. e. that the 

 fish is formed in the egg), and that they hatch 

 out fourteen days afterwards ; this same result 

 has been obtained by him for two seasons 

 following with very Httle variation. 



Again, he has observed that when the 

 temperature was 50° (in the spring of the 

 year) the eyes of the fish were visible in 

 twenty-six days, and that he hatched then 

 out in ten days afterwards. Lay it down 



* See report on experiments carried on "by Mr. Youl and 

 myself at tlie end of tlie book. 



