xlvi REPORT OF (TOMMISSIONER OF FISH AND FISHERIES. 



Several modifications of this box have been made, the most prominent 

 of these being that invented by Mr. Brackett, and used for the first tinie 

 in 1873. In this the box floats horizontally, but has the up-stream end 

 beveled, and the water striking against it produces an eddy under the 

 box, which causes a gentle agitation of the eggs. The details of this 

 and some other constructions will be found in Mr. Milner's article in 

 the appendix. None of them, however, can compare in simplicity and 

 efficiency with Seth (rreen's apparatus. 



In hatching the eggs of shad, much depends upon the temperature, 

 and when the water is above 80*^ it is very difficult to bring them for- 

 ward properly ; indeed, the fish appear to experience a loss of vitality, 

 and toward the end of the season apparently sound, ripe eggs fail to 

 develop, notwithstanding every care. When, therefore, the stream 

 reaches the degree of heat in question, the work is considered to be over 

 for the year. 



The hatching of icMte-fish, trout, salmon, i&c. 



An ingenious device has lately been patented by Mr. M. C. Holton, one 

 of Mr. Green's assistants, for the purpose of securing the development 

 of a large number of eggs from the trout, salmon, and white-fish in a 

 limited spacer Instead of placing a single layer of eggs in a long, nar- 

 row trough, he has prepared a can or box, of perhaps a foot square 

 and several feet in height. This is filled with shallow trays of about 

 half an inch in depth, with wire-gauze bottoms, on which the eggs are 

 placed, so that with twelve trays, having a surface of one square foot 

 each, he accommodates twelve times as many eggs as by the ordinary 

 method. The box is so arranged that a current of water is carried by a 

 covered pipe down the side of the can to the bottom and allowed to 

 enter at that point. Thecurreut in its ovei-flow^passes from the bottom 

 to the top, and the water circulates freely over the eggs. This arrange- 

 ment has the additional advantage that once a day, or oftener if neces- 

 sary, the trays can be taken out siugly, and any diseased or defective 

 eggs removed, thus improving the entire mass. 



The eggs of white-fish require a long time for their development, like 

 those of the salmon and trout needing from two to five mouths, accord- 

 ing to the temperature of the water employed. The lower the tempera- 

 ture the longer the period necessary. The general theory of the devel- 

 opment of eggs varies very much, according as they are smooth and 

 non-adhesive, or coated with mucus which causes them to attach to each 

 other or to other objects. The latter characteristic belongs to the Cypri- 

 nidce in general, such as chubs and suckers, to the yellow perch, and 

 many other kinds, for which reason it is extremely difficult to hatch these 

 out. But little has been done in this country in that direction, and here 

 the European culturists have the advantage of us. I owe to the kindness 

 of Mr. Rudolph Hessel, one of the best of the German pisciculturists, 



