284 MARKETABLE BRITISH MARINE FISHES 



tude and season, in cold water. At a temperature of 45^ F. the 

 eg|,^s hatched in twelve days at the Marine Station at Granton, 

 and in thirteen da}'s at about the same temperature in the United 

 States, while at 38° they were not hatched till the 20th day. 



The newly hatched larva is a little over 4 mm. in length 

 (o*T inch). With other species nearly allied such as whiting, 

 haddock, it agrees in the fact that the gut ends behind the yolk 

 at some distance from the edge of the fin-membrane ; while it 

 differs from these other species in having four bands of black 

 pigment on the body, one at the region of the pectoral fins, one 

 at the hinder end of the yolk, two on the tail. There is no pig- 

 ment on the fin-membrane. In larvse a little older the fin-mem- 

 brane instead of being flat throughout its length expands into a 

 wide bladder over the head : this disappears again at later stages. 

 Fig. 56, p. 103 , shows the character of the larva when ten days old, 

 but the limit of the bladder over the head is not indicated. 



Sars investigated the growth and development of the young 

 cod very carefully in the neighbourhood of the Lofoten Islands 

 in 1866 and 1867. In the former year he commenced his obser- 

 vations on May 7th, when he found that the spawning was 

 finished, and large numbers of fry were hatched. On May 20th 

 he was able on a calm day to see numbers of the fry near the 

 surface of the water ; they were about one-third of an inch in 

 length, and were very transparent. All that could be seen 

 distinctly from a boat was the comparatively broad head with 

 the eye projecting on each side, while the rest of the body 

 appeared like a fine thread vibrating constantly. These little 

 fry were feeding on very minute crustaceans, which swim near the 

 surface. On June 12th he had another opportunity of watching 

 the young cod fry in the sea. They were considerably larger, 

 measuring nearly an inch in length, and had to some extent 

 advanced from the larval or primitive condition to that of a 

 perfect fish. The primitive fin which runs unbroken round the 

 hinder end of the body had partly divided into the first two of 

 the fins on the back which are seen in the grown fish, and the 

 characteristic barbel on the chin had begun to show itself as a 

 little projection. 



After this bad weather set in, and for some days Sars was 

 unable to make observations in the sea. On June 23rd he found 

 a few of the }-oung cod, but the majority had disappeared. On 



