26 THE PELAGIC STAGES OE YOUNG FISHES. 



and twelve to fifteen small black dots in the posterior part of the eye. 

 The caudal end is entirely free from pigment for a considerable distance. 

 The pigment-cells of the body have also diminished somewhat in number, 

 but may still be said to be disposed in two lateral rows. The same clear 

 unpigmented cells are seen scattered over the yolk-sac. 



A still further reduction of pigment is noticeable in specimens examined 

 immediately after hatching, the black dots having entirely disappeared from 

 the yolk-sac (Figs. 6, 7). The dots of the eye are a little more numerous, 

 and usually blacker. The fin folds are wholly free, or nearly so, from pig- 

 ment. The black spots scattered rather sparingly along each side of the 

 body vary much in size and shape, presenting generally a coarse dendritic 

 form. In this stage it is usual to find only a single large black spot in front 

 and between the eyes, and a larger number of spots on the anterior than on 

 the posterior half of the body. In Fig. 6 are seen a few pale yellow spots on 

 the yolk-sac and anterior half of the body. In drawings of an earlier date 

 these spots do not appear ; but they were most likely overlooked, as they 

 are quite inconspicuous. The entire surface presents a rough aspect due to 

 peculiar granular cells. 



Characteristic of this species, as well as of Motella mmtclla * and Gadus 

 morrhua,^ is the termination of the alimentary tube on the side of the ven- 

 tral fin-fold, instead of at its margin. J The canal appears to open to the 

 exterior, but we are not positive that this is so at this stage of develop- 

 ment. No external opening appears in M. musldla, according to Brook, until 

 a much later date. 



The following measurements are from the specimen shown in Fig. 6 : — 



Total length 2.30 mm. 



Length of yolk-sac .75 " 



Width of yolk-sac 375" 



From yolk-sac to vent .12 " 



Vent to tip 1.20 " 



Height at middle .00 " 



Width of head 325 " 



The yolk-sac, seen from above or below, has an ovoidal form. 

 Figs. 10 and 11 represent the young fish about twelve hours after hatch- 

 ing. The pigment-dots have increased in number and size in the eye until 



* Brook, lor. eit., p. 304, 



f Ryder, John A. "A Contribution to the Einbryography of Osseous Fishes," p. 78. 

 % Agassiz (Young Stages, etc., Part HI. p. 290) calls attention to the same peculiarity in the young 

 Spanish Mackerel {Scomberomonm maculates, J. & G.). 



