MARINE TELEOSTEAN DEVELOPMENT. 95 



Vent. 



In the same way the posterior opening of the gut is not 

 produced by an inpushing of the outer layer (epiblast), but 

 is formed five or six days after hatching by the extension of the 

 internal lumen. At first the aperture is above the ventral 

 margin of the fin, but later the membrane is absorbed, and the 

 condition is almost that of the adult. 



Liver. 



Soon after the ear-chambers (otocysts) are formed the 

 ventral wall of the mid-gut shows an enlargement anteriorly, 

 and from this the liver arises as a solid proliferation. Into the 

 early organ a delicate canal passes from the fissure of the gut 

 the common bile-duct. By-and-by the liver becomes bifid a 

 right and a left lobe being distinguishable and in the midst a 

 spacious gall-bladder develops. The importance of the liver in 

 the larval fish is shown by its rapid growth into the yolk-sac of 

 the gunnel, and Wilson is of opinion that it is the medium for 

 the absorption of the yolk and periblast. 



Swim-bladder. 



From the dorsal wall of the alimentary tract the swim- 

 bladder is given off as a very thick-walled diverticulum which 

 presses upwards against the notochord, and remains for some 

 time connected by a fine canal with the gut. Before the 

 embryonic period ends, however, the duct atrophies in the forms 

 under consideration. 



In recent years considerable attention has been devoted to 

 the artificial hatching of sea-fishes, especially since their life- 

 histories have been more accurately known. In the Trawling 

 Report of 1884 one of us suggested that efforts might be made 

 in our country to augment the " soles, turbot, brill, and other 

 flat fishes," and perhaps also " the cod and other round fishes." 

 " Such an experiment, scientifically carried out, would give 

 a valuable basis for future legislation, tend to increase our 

 knowledge of the food-fishes in a remarkable degree, and would 



