LIFE-HISTORIES OF THE COD AND WHITING. 13 



line are still visible. The black pigment corpuscles along the sides often present a 

 more or less longitudinally linear arrangement. No scales are developed. A minute 

 papilla in the median line of the mandible indicates a barbel " (M'Intosh). These 

 remarks apply with equal force to the 24-25 mm. stage (fig. 15). 



Numerous lesser details may be noticed by a comparison of figs. 13, 14, and 15. 

 These three figures should be sufficient to ensure identification at any stage up to 

 25 mm. or more. 



From this stage onwards, Prof. M'Intosh thus described the young whiting.* He 

 figures the young fish at 26 mm. (pi. vi. figs. 1 and 2), at 30 mm. (fig. 3), and at 

 40 mm. (fig. 4), and carries his description up to the stage of 70 mm., after which the 

 adult characters are assumed. 



It has already been noted that the early cod is, at the same size, at an earlier stage 

 in development than the young whiting. This was evident in the stages up to 9 mm., 

 and is strikingly illustrated by a comparison of figs. 1 2 and 6. Again, the figure of a cod 

 at 11 mm. may be compared with figs. 13 and 14, and in some respects it is at an earlier 

 stage than the whiting of 9 mm. To this rule there is one exception, namely, the 

 barbel. This organ can be first clearly made out at about 10-11 mm. in the cod, 

 whereas it does not make its appearance in the whiting till a length of 19-20 mm. is 

 reached. This is a very marked exception, and one is tempted to connect it with the 

 fact that whilst the cod retains its barbel throughout life, in the whiting it is vestigial 

 only, and forms an " embryonic " organ. 



Apart from differences in pigmentation, the young whiting from 15 mm. upwards 

 can at once be distinguished from the young cod, and probably from all other gadoids, 

 by the condition of the anal fin and the forward growth of the anus. The differences 

 of external body-form are sufficiently striking, but in this, and especially in the pro- 

 portional sizes of various parts, it is very dangerous to draw conclusions from spirit- 

 specimens alone. We are safe to notice, however, that the head is proportionally 

 larger and heavier in the young whiting up to 25 mm. than in a cod of a similar size, 

 the reverse condition holding in the adult. 



Fig. 15 has an outline of the body much nearer that of an adult cod than whiting, 

 so that the whiting may be said, in this and other features, such as the presence of a 

 barbel, to pass through a " cod" stage. 



Lastly, in pigmentation (black) there are important differences. 



In the larval and early post-larval cod are the transverse bars, diagnostic of the 

 species, and the external pigment-line of the lateral line. This appears posteriorly very 

 early and progresses forward gradually, and is a constant character throughout the 

 stages here described. 



In the whiting, on the other hand, the internal supra-neural and sub-notochordal 

 lines, the scattered specks over the fin-membranes and over the post-anal part of the 



* Fifteenth Report Scottish Fishery Board, pp. 202, 203. 

 VOL. XL. PART I. (NO. 1). C 



