188 



Part III. — Fifteenth Annual Report 



eggs), as this flat-fish spawns on the offshore banks at a considerable 

 depth. Several forms of eggs, obtained in tow-nets, were successively 

 described as those of the turbot, the misleading features being chiefly the 

 correspondence in size with such eggs that were found in the ovaries of 

 ripe turbot. 



On board a north sea trawler, Holt succeeded in getting turbot eggs 

 that had been fertilised artificially, and he was thus able to give the first 

 description of the development of this egg and its larva (Jour. Marine 

 Biol. Ass., vol. ii. p. 399). 



Later (in 1893) Canu* obtained turbot eggs on the French coast, and 

 was able to supplement Holt's records. 



In 1895 M'Intosh f described the development of the turbot egg, and 

 particularly the larva?, of which some very fine coloured drawings were 

 given. 



Ehrenbaum \ has later described and figured the turbot eggs and larva? 

 at Heligoland Marine Station. 



It was first observed by Holt, and later by Canu, that the turbot egg 

 sinks to the bottom when the embryo is formed. I have found the same 

 peculiarity with eggs dealt with at this station, and I am able to sup- 

 plement the mere statements already referred to by records of some 

 observations that I made on eggs while developing in the hatching ap- 

 paratus. 



The turbot eggs had been artificially fertilised on the west coast (at 

 Girvan) and sent by rail to Dunbar ; on arrival here the development 

 w T as far advanced (in the multicellular stage), and as the eggs had 

 been much exposed to changes of temperature and other hardships, I 

 found the specific gravity so much affected, that records of it were mis- 

 leading. But I have reason to think that it does not exceed 1024*5 

 shortly after fecundation. When 48 hours old I found the specific 

 gravity increased to 1026 "8 in water of 12° C. At this time the embryo 

 reached across the egg, measuring 1*0 mm. in length. Aiter this the 

 turbot egg sinks in ordinary surface water ; but, as I have never found 

 their specific gravity to exceed 1028*0, these eggs will not sink to the 

 bottom where the sea is sufficiently deep ; perhaps 30 fathoms or more. 

 This circumstance will therefore much reduce the chances of the turbot 

 eggs that are spawned in the sea, as it is probable that most of those eggs 

 that sink down and rest on the bottom, will succumb. The newly 

 hatched turbot measures about 3*0 mm. ; it has a hardy appearance, and 

 is richly pigmented; this is well shown in Mlntosh's fig. 11, PI VIII., 

 where the true brick-red colour is represented. The larva? grows rather 

 quickly while the yolk is being absorbed, and the pigment is much 

 increased, particularly along the seam of the dorsal marginal fin. The 

 tail remains almost free from pigment. When the yolk is absorbed the 

 larva? measures about 5*0 mm. in length. 



During the last season (in 1896) I made an experiment with the 

 rearing of turbot during the post-larval stage, and the same apparatus 

 was used that had proved so successful with the plaice. A couple of 

 dozen larva?, which had absorbed the yolk, were placed in the jar, and 

 food was provided as before by tow-net collections. 



During the first three days the larva? appeared at all levels in the jar, 

 and were eagerly in search of food. Only in one case I found remains of 

 diatoms in the stomachs that were examined ; the form observed was the 



* Annahs Station Aquicole de Boulogne-sur-Mer. 

 t Thirteenth Annual Report of the Fishery Board, Part III. p. 227. 

 X Eier u. Larven v. Fischen d. deutschen Bucht., p. 282. Kiel und Leipzig, 

 1897. 



