BULLETIN OF THE UNITED STATES FISH COMMISSION. 187 



An exit tube, the lower extremity of which extends a short distance 

 below the neck of the bottle, provided for the escape of the water. 

 Whilst this form of apparatus had been devised by me in connection 

 with the experiments on retardation above referred to, I had no sooner 

 fixed upon the apparatus than I felt at once I had arrived at the solu- 

 tion of the question of automatic separation of the dead from the living- 

 eggs. An eight-ounce wide-mouthed glass jar, such as is used in the 

 National Museum for holding alcoholic specimens, was fitted up as in- 

 dicated (Fig. 3). 



Six thousand shad eggs were placed in this apparatus and a current 

 of water turned on and regulated. The movement of the current estab- 

 lished a regular rolling, boiling motion on the eggs, which brought all 

 in succession to the surface. The dead eggs remained there, forming 

 as they were freed from the mass a lawyer upon the upper surface of the 

 others. By pushing down the exit tube a suitable distance, I found 

 that the dead eggs were taken up by the escaping current, were by de- 

 grees drifted under the lower end of the tube, lifted through it by the 

 current, and swept out, leaving an absolutely clean mass of live eggs iu 

 the jar. 



This lot of eggs was successfully hatched, and at the time of hatching 

 not a dead egg was found in the bottle, nor do I think a live egg was 

 lost in the whole course of the experiment. 



The first experiments had been framed solely with reference to the 

 assumed slight difference in the specific gravity of the living and the 

 dead eggs. Attentive study of the movement of the eggs in the jar 

 showed a still more potent influence for separation than the difference 

 in the specific gravity. It is true there is a slight difference in this re- 

 spect, but it is hardly appreciate. The more important difference, and 

 that upon which the success of the apparatus depends, is the close ad- 

 hesion which exists between the living eggs, the effect being that the 

 live eggs rolling in mass are always in contact, even when they reach 

 the surface, and are by this adhesion carried around in regular sequence. 

 On the other hand, the dead eggs having once reached the surface, 

 their adhesion to the underlying layer of eggs is not sufficient to draw 

 them along with it in its regular movement; consequently when they 

 once reach the surface of the mass they remain there until they are 

 carried off by the exit tube. Several experiments made with different 

 lots of eggs gave uniformly the same satisfactory results. 



In May, 1881, the apparatus in actual operation was exhibited before 

 a meeting of the Biological Society held in the basement of the Smith- 

 sonian Institution. These experiments were so decisive that I did not 

 hesitate to recommend and urge the adoption of the new method in the 

 work of the United States Fish Commission. 



In the spring of 1882 it was determined to convert the old Armory 

 building into what is now known as the Central Hatchery and Dis- 

 tributing Station. Prof. S. F. Baird was pleased to manifest his confi- 



