866 BULLETIN OF THE BUREAU OF FISHERIES. 



At the end of a few weeks of captivity our prisoners began to feed. To them 

 were distributed once a week large pieces of plaice at the rate of about half a fish 

 the size of the hand to each turbot. This ration may seem scant, but it was 

 purposely limited, we deeming that too great an abundance of food is not favor^- 

 able to the functions of reproduction. It is probably to excess of feeding 

 that must be attributed the failure of attempts to make the turbot spawn in 

 captivity. In order to keep the basins free of putrefying food substances we put 

 with our turbots a conger eel and a dogfish long since acclimated to life in cap- 

 tivity. These fishes, well known for their voracity, were employed as scavengers, 

 in which capacity they did good service. Our turbots, in captivity since Feb- 

 ruary, began to spawn in July. 



We do not know yet whether individuals that have spawned in captivity 

 and survived one season will spawn the following year. We will not know this 

 until in July next. In any case it does not seem to us very important to know 

 whether it is necessary to keep the same brood stock for one or more years, since 

 fish captured only six months previously had ample time to get acclimated 

 and have given excellent results. Let us add that it seems to us very imprudent 

 to capture breeders onl}^ a few weeks before the spawning time. Not yet 

 acclimated, they might exhibit phenomena of ovular retention, which are in 

 most cases fatal. 



The first eggs were laid on July i8, and were soon followed by four other lots. 

 The dates of the consecutive spawnings were July i8, 21, 28, 29, and August 3. 

 These lots of eggs numbered thousands and thousands, all normal and normally 

 fertilized. A certain number only were carefully gathered by means of plankton 

 nets and transferred to the incubation apparatus. An essential feature of this 

 apparatus is continuous agitation, which is a very important thing in incubation, 

 keeping the egg free of sediment and thus preventing asphyxiation. Dannevig, 

 among others, at the station of Dunbar had already employed a complicated 

 apparatus which provided continuous agitation. 



The apparatus used by us was that of Fabre-Domergue and Bietrix modified, 

 which apparatus is in itself a modification of that constructed by Browne at the 

 laboratory of Plymouth to preserve pelagic organisms alive. It consisted of a 

 receptacle in which a plunging disk rose and fell by means of a special contrivance. 

 In the apparatus of Fabre-Domergue and Bietrix the somewhat violent agitation 

 produced by the vertical motion of the disk is replaced by a helicoidal movement, 

 the disk being obliquely fixed on a vertical rotating axis and thus working like 

 a screw. The apparatus is composed of 4 glass barrels of 50 liters capacity, 

 each supplied with a revolving disk, and the 4 disks are worked by a small hot- 

 air motor of -^ horsepower. 



