[3] OPERATIONS AT CENTRAL STATION. 881 



peated when the hatching begins, gives us the means of arriving accu- 

 rately at what had been previously very roughly and inaccurately 

 estimated, namely, the percentage of loss during iucubatiou. 



The automatic action of the jars is sufficient to separate entirely the 

 dead eggs from the living, so that when the hatchiug period approaches 

 the fish-culturist in charge has only to deal with a mass of living eggs, 

 the dead eggs being separated from them and carried off through the 

 exit-tube from each jar, or are collected and fed to the fish in the differ- 

 ent aquaria. 



In order to provide for the collection of the young fry, when hatch- 

 ing begins, the discharge from the jars, instead of passing directly into 

 the waste, is first conducted into aquaria conveniently placed along 

 the center of each hatching table. To prevent overflow of this and 

 loss of fish, a siphon is placed in each of the aquaria, the shorter end 

 being terminated with a large wire cage covered by a bag of muslin, 

 the longer end being immersed in a glass of water. The effect of this, 

 when once a current of water is started, is to render the action of the 

 siphon automatic and self-adjusting. Free exit is thus su]iplied for the 

 water, and the straining surface of the muslin bag is so large as to pre- 

 vent any perceptible suction through it, so that we are thus enabled 

 to collect and hold the young fish in the receiving vessels until they 

 have accumulated in quantity and for convenience of shipment. The 

 arrangement of one of the tables for hatching and collecting is shown 

 in detail in Plate IV. 



Thus equipped, the Central Station of the United States Fish Com- 

 mission entered upon the work of propagation. 



2. PROPAGATION. 



Shad. — The methods employed in the transportation of eggs from the 

 collecting stations on the river, as well as the apparatus used in hatch- 

 ing them at the station were novel, and a bold innovation upon the 

 methods and apparatus in use up to that time. Though both had prom- 

 ised well in the experimental investigations conducted the x>revious 

 season, they were now to be subjected to the test of practical ai)plica- 

 tion upon a large scale; and I am glad to be able to report that the re- 

 sults of the work done during the season justified our expectations. 



The Navy-Yard Station and the Fish Hawk being both available for 

 the work of shad propagation on the Potomac, it was determined to es- 

 tablish three independent stations, each drawing its supply of eggs 

 from an independent section of the river. The Fish Hawk was stationed 

 at Occoquan, and the lower section of the river, from Stump ISIeck to 

 Stony Point, assigned as its theater of operations. The upper section 

 of the river, extending from Moxley's Point to Washington, was assigned 

 to the Navy-Yard Station, the Lookout being detailed for the collection 

 and transportation of the eggs to the station. The middle section of 

 the river, extending from Chapman's to Ferry Landing, was occupied 

 S. Mis. 46 50 



