LIFE-HISTORIES OF THE COD AND WHITING. 7 



pigment in the peritoneal dorsal wall of the abdomen, especially above the swim- 

 bladder, which at this stage is nearly circular. 



When the mouth is closed the mandible forms a very prominent angle, and its 

 lower border is very nearly vertical. This character, which is more or less marked in 

 most gadoid and other pelagic larvae, is probably to be traced to the method of feeding. 

 A gaping mouth at the extreme front end with no inclination upwards or downwards 

 would best subserve the capture of pelagic Crustacea, as well as the function of 

 respiration. The coloration at this and later stages consists of a diffuse greenish- 

 yellow tinge, especially prominent* over the head and back. 



In fig. 2 a length (in spirit) of 5*2 mm. is reached. The external pigmentation 

 has increased, the dorsal elements of the post-anal bars approaching one another. A 

 few spots upon the mandible and the commencement of a row along the lateral line 

 may be recognised. The internal pigmentation has increased, and includes additions 

 on the liver and pericardium. This stage carries the series on to fig. 3, in which it is 

 evident that considerable progress has been effected. This stage has been described by 

 Prof. M'Intosh.1" In the external pigmentation we may notice the first appearance 

 of a fine mid-ventral line along the median edge from the anus to the throat. The 

 dorsal elements of the two larval post-anal bars have now united to form a median 

 dorsal line. Apart from the few scattered spots on the head, the young cod now has 

 an external pigmentation of four more or less prominent longitudinal lines, a mid 

 dorsal from above the anus to the tail, a mid ventral from the throat past the anus 

 to the tail, and a pair of short lateral-line rows in the post-anal portion. Whilst the 

 transversely-barred condition of the larval cod is almost unique, this longitudinally- 

 barred condition of the post-larval stage, whatever its significance, is of very general 

 occurrence in young teleosteans. 



So far as is possible, the pigment of the bars is, as it were, made use of to form the 

 lines ; the rest disappears. 



At 7 mm. (spirit), fig. 4, the fin-rays are very evident in the tail, whilst the 

 marginal fin is reduced. The external pigment system is similar to that in the preced- 

 ing stage, but intensified. A characteristic blotch just behind and over the pectoral fin 

 is evident. It is to be noticed that the dorsal and ventral lines do not here, nor at any 

 stage, reach actually to the tail, but end suddenly at some distance therefrom. The 

 internal pigment is much as before, and tends to spread over the swim-bladder, which is 

 still nearly spherical. 



Figs. 5 and 6 carry the series on by easy stages. Increase in intensity of the pig- 

 mentation is marked. In fig. 6 the dorsal and ventral lines are very marked, and the 

 lateral lines have extended. In this stage the notochord no longer reaches to the tip 

 of the caudal fin, which now becomes pronounced in shape. The internal pigment has 

 become very dense in the abdominal cavity, and a line extends over the dorsal surface 

 of the neural cord. 



* Loc. cit., p. 818. t Loc. cit., p. 818. 



