BULLETIN OF THE UNITED STATES FISH COMMISSION. 63 



in bulk only such eggs the fry of which are able to swim out of the mass 

 of eggs when hatched, or are light enough to be thrown out by the 

 current of water. Ko objections on this score can be raised to this plan 

 for hatching ova of the whitefish {Coregonus albus), or of the shad {Alosa 

 sajridissima). 



Of the several appliances which have been invented for hatching eggs 

 by the bulk method, those most prominent, and which are undoubtedly 

 the best, are the Mather & Bell cone, as improved by Major Ferguson, 

 and the Chase hatching-jar. 



The cone has been used exclusively for hatching the shad, while the 

 jar has been confined to the whitefish work, with the exception of a 

 single experiment wi'oh shad-eggs, where it was found to work very well, 

 but must be tried still further before it can claim equality with the cone 

 for shad work. 



The cone, too, with the " Clark" gate attachment, would, in all j)rob- 

 abilitj", equal the jar for hatching eggs of the whitefish, but has not been 

 sufiflciently tested in this direction to warrant its introduction without 

 further experiment. 



The jar, although but recently introduced, has largely displaced the 

 hatching devices for whitefish work hitherto in use, and, when its merits 

 are more fully understood and appreciated, will, I think, entirely super- 

 cede all other appliances for the work in question. With its use one 

 man can take care of 20,000,000 ova, and thus its great economy, as 

 compared with any hatching-box ever invented, will be readily apparent. 

 This great difference in its favor may be credited to the fact of its being 

 so constructed and operated as to collect for the most j)art the eggs of 

 coufervoid growth at or near the surface of the mass of eggs, whence 

 they are easily removed. Thus it will be seen that they are "partial 

 separaters," but not " self-pickers." 



But this partial separation of the dead eggs is a merit of no small 

 proportions, as but little time is required for their removal when massed 

 together, while the small percentage of dead eggs remaining unseparated 

 is rendered ijowerless to harm the living ones by the constant current of 

 water, which keeps the whole mass of eggs in ever-changing motion, 

 and thus protects the latter from the contaminating influences of the 

 former. It may be stated, as an actual fact, that where water of a tem- 

 perature not exceeding 40° F. is used, in consequence of which the cou- 

 fervoid growth is comparatively slow, a large percentage of dead eggs 

 may be allowed to remain or collect in a jar without jeopardizing the 

 lives of the remainder ; but the practice of removing all extraneous 

 eggs collecting at the surface is to be commended. 



The method employed by Mr. Chase, inventor of the jar in question, 

 for removing these eggs, is to augment and thereby strengthen the cur- 

 rent of water in the jar to that degree necessary to Ibrce the mass of 

 eggs upward until the surface is on a level with the mouth of the jar, 

 the gate being raised in the mean time to allow the surface eggs to float 



