40 FISH-CULTURAL ASSOCIATION. 
separation than the difference in the specific gravity. It is true 
there is a slight difference in this respect, but it is hardly ap- 
preciable. The more important difference, and that upon which 
the success of the apparatus depends, is the close adhesion which 
exists between the living eggs, the effect being that the live 
egos 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 thev once reach the surface of 
the mass they remain their until they are carried off by the exit 
tube. Several experiments made with different lots of eggs 
gave uniformily 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 Smithsonian Institution. These experiments were so de- 
cisive that I did not hesitate to recommend and urge the adop- 
tion 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 Distributing Station. Professor S. F. Baird was 
pleased to manifest his confidence in the success of the new 
form of hatching apparatus by authorizing me to equip the 
station with them. The working form of apparatus not having 
been then even designed on paper, it was not possible to prepare 
the drawings and to have the jar complete in all details ready 
in time for the shad-hatching season. An improvised form was 
devised in which cork stoppers were substituted for the screw 
cap and metal tops employed in the form now fixed upon. Ten 
tables suitably planned to receive the waste water from the jars 
and carry it off from the building were constructed; the pipes 
for the distribution of water supply to the tables were introduced, 
and the station was equipped with 300 of the jars. Each jar 
having a capacity of 60,000 to 70,000 shad eggs, gave a total 
hatching capacity to the station of 21,000,000 eggs at one time, 
or 900,000,000 for the entire shad-hatching season. This was, 
