50 AMERICAN FISH CULTURE. 



flow beneath but over the top of the strips. The strips 

 should also be exactly the same width, so that the ripples 

 over them may be uniform. They should be made of half- 

 inch pine, and should slip out or in so that they can be 

 removed at one's option. The gravel should be about the 

 size of peas, and if possible of some uniformly dark tint, 

 that the eggs lying on it may be the more easily examined 

 It should be thoroughly washed, by shaking and turning it 

 in a basket in clear running water, and again, by stirring 

 it after placing it in the hatching-trough, commencing at 

 the upper end of the trough and stirring it in each suc- 

 cessive nest until the water runs clear. Mr. Ainsworth is 

 so careful as to boil the gravel, that he may destroy the 

 eggs or larvse of insects that may possibly remain after the 

 gravel is merely washed. When there is sufficient fall 

 from the spring to admit of it, it is better to have the 

 hatching-troughs elevated about three feet, so as to allow 

 of an easier examination of the eggs, as it is no small labor 

 to attend to them on the ground if one has four troughs to 

 go over daily during the incubation. 



A few simple instruments are required by the fish cul- 

 turist. For examining the eggs a small vial, two or three 

 inches long and a half-inch in diameter, is used. The eggs 

 are taken up with a small pair of pliers and dropped into 

 the vial nearly filled with water, which, after replacing the 

 cork, is held horizontally before the light and turned so as 

 to present different views of the eggs. The pliers can be 

 made either of single or double wire; if of the latter, a small 

 bowl can be formed at the end of each prong by bending 



