184 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



fish in an aquarium at Wasliington deposited a string of eggs 88 iuclies 

 long, 4 inclies wide at one end and 2 at the otlier, whose weight after 

 fertilization was 41 ounces avoirdupois, while the weight of the fish 

 before the escape of the eggs was only 24 ounces. 



A cavity extends the whole length of the egg mass, its walls -being 

 formed by tlie 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 of water on the inside of the mass. 



The egg-string is quite light and resilient or springy, the least agita- 

 tion of the water causing a quivering motion of the whole mass. 



The diameter of the egg is -1-3- inch. The quantity can not be easily 

 measured, but the number is approximately 28,000 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 ajiparatus. 



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

 Commission. One season, at Central Station, Washington, D. C, 130 

 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 March 10 and continued till April 3, 

 and 98 strings, containing nearly 1,000,000 eggs, were deposited. 



Tlie eggs are hatched in the automatic shad jar, provided with a cap 

 of fine-meshed wire netting; the usual inflow tube is retained, but the 

 sii)hon tube is withdrawn, the water escaping over the top of the jar. 

 The amount of water circulation is not great enough to force the mass 

 of eggs to tlie upper part of the jar or to give much motion to them. 

 They are lighter than shad or whitefish eggs, and when put in rapid 

 motion to dislodge adhering sediment they would clog the outlet tube 

 if the ordinary method of manipulating this jar were employed. 



The eggs from several fish may be placed in one jar. They perhaps 

 need as little care as any eggs handled by fish-cult.urists. When one 

 string of eggs or one lobe of a string dies it may be removed with a 

 small net, or the entire contents of the jar may be turned into a pan. 



The period of hatching vaines from two to four weeks, according to 

 the temperature. As the fry hatch, they pass over into tanks provided 

 with screened overflows, where they are held till i)lanted. The fry are 

 very hardy, and may be readily retained in aquaria for several weeks. 

 The percentage of eggs hatched is large. From one lot of 955,000, 

 754,000 fry, or 79 per cent, were produced. 



