294 REPORT OF THE COMMISSIONERS OF 



by a close season during its breeding period, it does not seem to diminish in any 

 waters where it is found naturally. At intervals, in some waters, even the best and 

 purest, an epidemic visits the perch tribe, and vast numbers are found dead in the 

 water and on the shores; but this does not appear to decrease the supply of healthy 

 fish in the water. The following description of the fish is taken from the " Manual of 

 Fish Culture," already mentioned : 



"The eggs of the yellow perch are among the most remarkable that have been 

 artificially hatched. The spawn is in one piece, a much elongated ribbon-like 

 structure, of a semi-transparent, light-grayish color. One end of the large egg mass, 

 corresponding to the anterior part of the roe, is larger than the other, and is bluntly 

 forked. The string is very long, but may be much compressed lengthwise by virtue 

 of its arrangement in regular transverse folds like the sides of a bellows or accordeon. 

 "When deposited the eggs are in a loose globular form, and after being fertilized and 

 becoming " water-hard " their mass rapidly becomes many times larger than the fish 

 which laid them. The length of the strings is from two to more than seven feet, 

 depending on the size of the fish. One fish in an aquarium at Washington deposited 

 a string of eggs eighty-eight inches long, four inches wide at one end and two at the 

 other, whose weight after fertilization was forty-one ounces avoirdupois, while the 

 weight of the fish before the escape of the eggs was only twenty-four ounces. 



" A cavity extends the whole length of the egg mass, its walls being formed by 

 the delicate membrane in which the eggs are imbedded. The cavity is almost closed, 

 small apertures occurring irregularly, which have the appearance of being accidental, 

 but may be natural, in order to permit the circulation cf water on the inside of 

 the mass. 



"The egg string is quite light and resilient or stringy, the least agitation of the 

 water causing a quivering motion of the whole mass. 



"The diameter of the egg is one thirteenth of an inch. The quantity cannot be 

 easily measured, but the number is approximately twenty-eight thousand to a quart. 



"The best method of securing the spawn is to place mature fish of both sexes in 

 suitable tanks with running water. The females selected should be those whose 

 external appearance indicates that the eggs are still undeposited. Spawning takes 

 place at night, and the eggs are naturally fertilized. Under proper conditions, it is 

 the exception to find unfertilized eggs. In the morning the eggs are transferred to 

 the hatching apparatus. 



"The eggs of this fish have been hatched at different stations of the Commission. 

 One season, at Central Station, Washington, D. C, one hundred and thirty ripening 

 females and about an equal number of males taken from the Potomac were placed in 

 aquarium tanks supplied with water from the city water-works. Spawning began 



