BULLETIN OF THE UNITED STATES FISH COMMISSION. 345 



to the scieuce of zoology, more especially in a field where that science 

 not only promises to supply many of the daily wants of the masses, but 

 where it has already accomplished a great deal. They are the men 

 who use .for investigations in the field of embyology the exceedingly 

 valuable scientific material furnished by the numerous stages of develop- 

 ment of fish which may be observed in practical fish-culture. We may 

 doubtless look for important communications relative to the results of 

 these scientific investigations. 



Bound this staff of scientists there has gradually been formed an en- 

 tire camp of officers who are thoroughly versed in the more mechanical 

 work of fish-culture and fish transportation. The catching of mature fish, 

 the impregnation of the eggs, the care of them during their development, 

 and the raising of the young fish can only be intrusted to experienced 

 persons, although a scientific education is not required for this work. 

 It is self-evident that any one who desires to carry on fish-culture on a 

 large scale must endeavor to obtain men who have had a good deal of 

 practice in that line. 



Let us now illustrate by two examples, the shad and the cod, what 

 different methods and aids the Americans employ for reaching the great 

 object in view, viz, a considerable increase of salable fish, cheap and 

 wholesome food for the masses, and thereby an improvement in the 

 condition of the common people. 



As soon as the shad is ready for spawning, about the month of April, 

 the officers in charge of propagation of this kind of fish go to those 

 places where large numbers of shad are found. To these places the neces- 

 sary apparatus is forwarded, and suitable locations are selected for 

 carrying on the work. 



The first object is to obtain mature fish of both sexes. These are 

 caught exclusively by night. Thus there were, in 1878, from 82 shad 

 obtained no less than 1,G05,000 impregnated eggs. For the develop- 

 ment of these eggs it is necessary that they remain in flowing water; 

 and as they are heavier than the water, and therfore sink to the bottom, 

 cone shaped glass or metal funnels are used, into which the water enters 

 from below through a narrow opening and flows out at the top through 

 a gauze covering. Thus a very large number of eggs may be kept in 

 a fresh condition within a comparatively small space, and may thus be 

 safely developed. By a small modification of this apparatus the same 

 current is used for separating the dead eggs and all impurities from 

 the healthy eggs; while the latter remain near the bottom, the former 

 are by the current carried towards the top and over the edge, and are 

 thus easily removed. 



In order to work a large number of eggs at the same time, Seth Green 

 many years ago invented a so-called " shad-box," which he kept floating 

 in the current, the water being freely admitted to the inside through 

 the front, which is of gauze, and placed in a slanting position. This 

 was doubtless a great improvement. In stormy weather, however, 



