THE HISTOEY OF FISH-CULTURE. 489 



plants ; the linen dries less rapidly, and facilitates the unpacking-, which, 

 in the other cases, requires much time and care. The Marquis of Yi- 

 braye, to whom the Sologne owes so many useful improvements, and 

 who has already introduced on his estates numerous trout produced 

 by artificial fecundation, has also made use, with advantage, of small 

 wadded cushions. When the eggs to be dealt with are very delicate, 

 and are to be transported during the summer, M. Millet sometimes 

 employs the little portable ice-box, of which we have already given the 

 description. 



As soon as the young fish have completely absorbed their umbilical 

 vesicle, that is to say, some weeks after the hatching, the author of 

 these curious experiments is of opinion that it is best not to try to 

 nourish them in captivity, but to dismiss them at once into the waters 

 where they will have to live, taking care,, however, to place them suit- 

 ably where they will find the spawn of frogs, lymneas, planorbis, &c. 

 They should commence at once to seek for their prey, and thus avoid 

 the suffering from change of water, of nourishment, and of liabits, to 

 which they will necessarily be subject, if raised artificially in basins 

 not communicating with the waters which they must inhabit. 



It is principally in the departments of the Eure, the Aisne, and the 

 Oise that M. Millet has put in practice these various methods. Affi- 

 davits emanating from the local authorities bear witness to the impor- 

 tant results which he has obtained. M. Millet has conducted, at the 

 same time, a series of delicate observations, which have already led to 

 some happy applications.* He has examined the action of salt or brack- 

 ish water on the eggs of fish which leave the sea to spawn in fresh 

 water, and he has seen that it is injurious to their development in 

 ordinary cases, which gives the practical reason of the emigration of 

 these animals. Nevertheless, salt, which would destroy the healthy 

 eggs, lias the singular property of healing them" when attacked by 

 white spots. These spots, which probably spread from the surface to 

 the center, and would lead to the destruction of the eggs if allowed to 

 increase, disappear in water very slightly salted ; and when they are 

 taken in time, the young fish may thus be saved. It results also, from 

 the observation of M. Millet, that the mortality of the eggs always 

 reacUes its maximum at the epoch when the embryo begins to form ; 

 accordingly he advises transporting them only when the eyes become 

 visible, or rather immediately after the fecundation. He has remarked, 

 finally, that the white spots on the one band, and the sea-weed and 

 byssus on the other, attack much more rarely the eggs of trout and 

 salmon, at a low temperature, than in one which exceeds fifty-four 

 degrees. 



Here terminates the rapid Exposition of the applications furnished by 

 zoology to the economy of ponds and water-courses, and of the prog- 



* Cotnptes-rendua of the Academy of Sciences, vol. xxxviii, session of December 



26, 1853. 



