BULLETIN OF THE UNITED STATES FISH COMMISSION. 211 



timeter thick and 1.5 centimenters broad, runs all round the inner 

 side of the vessel. On this flat edge rests the second vessel, which is 

 20 centimeters deep, and whose bottom is perforated by numerous very 

 small openings. Up to a height of 5 centimeters the side of the inner 

 vessel rises perpendicularly ; for the next 5 centimeters it is inclined 2 

 centimeters towards the inside, and above this it again rises perpen- 

 dicularly. The upper edge, 2 centimeters broad, is bent over. The 

 second division of the inner vessel, showing in its section an angle pro- 

 jecting towards the inside, is perforated along its entire circumference, 

 just like the bottom. 



The application of this apparatus will easily be understood. Through 

 the tube on the outside the water flows in, entering the bottom of the 

 outer vessel ; through the perforated bottom of the inner vessel it enters 

 into this and moistens the eggs, which may cover the bottom to the 

 height of 5 centimeters; the water now goes through the perforated 

 part of the circumference of the inner vessel, and passes again into the 

 outer vessel; but it must rise 5 centimeters higher, in order to flow out 

 through the outlet of the outer vessel. In one minute 3 liters of water 

 can pass through the apparatus. 



Fig. 3. 



The advantages of this construction will be readily perceived. In the 

 first place the upper frame, which prevents the inspection of the eggs, 

 which easily becomes too tigbt, and which injures the young fish when 

 they press against it, is dispensed with. The perforated wall of the 

 inner vessel lets as much water flow off into the outer vessel as flows 

 in through the perforated bottom. But as the outlet of the outer vessel 

 is still 5 centimeters higher than the perforated ring of the inner vessel, 

 and consequently there must still be a depth of water of 5 centimeters 



