868 BULLETIN OF THE BUREAU OF FISHERIES. 



yolk sac, and following in this the excellent advice given by Mr. Edmond Perrier 

 in 1896, at the Congress of Fisheries at Sables d'Olonne, and a little later, in 

 1898, by Mr. Fabre-Domergue, we began the feeding of our young larvae. Their 

 diet was composed of live plankton collected in the open by means of fine-meshed 

 nets, and carefully sifted upon arrival at the laboratory through very fine sifting 

 silk, for the purpose of eliminating the organisms which might constitute a 

 danger by their size or their nature. One distribution of plankton was made 

 every day, and in great abundance. Moreover, the agitation of the water 

 maintained the plankton alive, and the young fry had consequently always in 

 reach a fresh live food as varied as under natural conditions of their life. Toward 

 the fourteenth or fifteenth days the last trace of the sac disappeared, and about 

 the eighteenth or twentieth day the critical period might be considered as passed. 

 The young larvae had at that period taken the peculiar shape characterized by 

 the widening of the head, and they fed normally. 



For the retention of the larvae after the beginning of the resorption of the 

 yolk sac, i. e., during the critical stage, two things are necessary: (i) Continuous 

 agitation of the water, and (2) appropriate food. Continuous agitation of the 

 water is incontestably very useful in the incubation of the eggs and the normal 

 life of the larvae up to the time when they begin to feed, but during these periods 

 it is not, as later, absolutely indispensable. 



We have, in fact, found at St. Vaast, on the one hand, that the eggs which 

 were left in our hatching basins developed there and hatched normally , and the 

 larvae did very well until after the disappearance of the yolk sac ; on the other hand, 

 the same facts were observed in the hatching aquaria. But what we did not 

 accomplish, and we can not insist too much on this point, was to make larvae live 

 even a few hours, though offering them plankton, under these conditions after the 

 disappearance of their yolk sac. It is at this time, we believe, with all who have 

 undertaken marine pisciculture, that continuous agitation of the water is abso- 

 lutely necessary. Without it the young fish is never in the presence of its food, 

 it weakens, falls to the bottom, and dies of hunger. 



As to feeding, let us recall that the fry were very precocious, and began to 

 feed even before the complete disappearance of the yolk sac. The objection 

 might be raised that plankton as the basis of food for the larvae can not be con- 

 sidered for a moment where breeding on a large scale is to be undertaken. It 

 may be said that on certain days storms disturb the sea, and the water being 

 full of ooze and sand, collecting is impossible. We believe that we can say that 

 the period during which plankton will be necessary is precisely during the 

 season of the year in which storms are most rare (from July i to September 15, 

 at the latest, for the region of St. Vaast- la-Hougue) . Should there be storms, 



