THE HISTORY OF FISH CULTURE, 557 



They are especially valaahle because of their adaptation to ponds and 

 even stagnant waters attaining- a high degree of heat. In addition to 

 their value as food for man, they will be of great utility in affording a 

 supply of food for those piscivorous fishes it is desirable to propagate ; 

 being, it is said, in a considerable degree herbivorous, they can exist in 

 large numbers in the ponds with black bass, glass-eyed pike, or the mus- 

 kellunge, without reducing the original food of these flshesiu the waters, 

 and, of course, increasing it in a considerable degree in the presence of 

 their own young. 



The procuring of cheap food for the fishes in the troughs, in the nur- 

 series and. the ponds, has been obtained, to a considerable extent, in this 

 way in Germany and Russia, and, it may be, would be found to answer 

 for our brook-trout. 



Another fish, the introduction of which is desir'ible but whose propaga- 

 tion may be left entirely to nature, like that of the black bass, is the 

 gouranii, {Osphromenus olfax,) a species that is prolific, attains consid- 

 erable size, of most excellent flavor, and is especially advantageous 

 from the the fact that it is adapted to the warm water-ponds of the 

 warmest temperate and subtropical regions. It can be readily intro- 

 duced in the southern portions of the United States from China or from 

 Algiers ; in both countries it has been introduced, originating in the 

 Malaccan Islands. (See Department of Agriculture Report, 18G6, p. 417.) 



Although the loss of eggs before hatching has been reduced to an in- 

 considerable minimum by means of improved methods of im])regnation 

 and care during hatching, still there are many things to be accom- 

 plished before any high degree of perfection in the culture of fishes will 

 be attained. One of the most important desiderata is the prevention or 

 cure of the omnipresent confervaceous growth, {Achlya prolifera.) Nu- 

 merous experiments have been tried by men skilled asfish-culturists 

 and chemists without accomplishing anything that receives general 

 application and approval. The application of salt-brine has been advoca- 

 ted.* Experiments have also been made with solutions of acids and 

 alkalies. 



The apparatus for packing eggs in boxes covered with ice and moss, 

 so that the low temperature may retard the growth of the confervie, 

 has been described on page 547-. 



At Mr. N. W. Clark's hatching-house the eggs of the white-fish during 

 the past winter have been daily rinsed free from adhering sediment and 

 the developing i)arasites by agitating the trays containing the eggs in a 

 shallow pan of water. This, though it may appear a rather violent 

 treatment of the eggs, has been kept up throughout the winter without 

 apparent injury, and a large percentage of young fishes has resulted 

 from the eggs thus treated. 



A uniform system in the estimation of the numbers of eggs, and con- 

 sequently a more reliable estimate of the percentages hatched, has been 



* On page 174 will be found an account of the metliod employed to clean the eggs 

 of the Salmo quinnat from this foul growth by meaus of sand aud water. 



