MANUAL OF FISH-CULTURE. 227 



Development takes place in water ranging in temperature between 

 33° and 5r)0 F., tlie time of incubation varying from about 40 clays at the 

 former temperature to 11 or V2 days at the latter. Sudden and extreme 

 variation between the temperature limits mentioned had little or no 

 effect except to retard or accelerate the hatching in accordance with 

 the rule just mentioned. When water of a temperature lower than 

 33° F. was used many of the embryos were deformed. The degree of 

 salinity of the water does not appear to exert much influence upon the 

 hatching of the eggs. 



THE SAND-DAB AND FOUR-SPOTTED FLOUNDER. 



Besides the flatfish or winter flounder, two other flounders have been 

 artiflcially hatched, on a small scale, at Woods Hole; these are the 

 sand-dab {Bothus maculatus) and the four-spotted flounder {ParaUchtJiys 

 ohlongus). The eggs of both fish are buoyant, and deposited in May. 

 Those of the former are .f^ inch in diameter, and of the latter -,h^ inch. 

 The iDeriod of incubation at a tem]ierature varying from 51° to 54° F. 

 is about 8 days. 



