12 THE PELAGIC STAGES OF YOUNG FISHES. 



There is considerable variation in the width of the embryonic fin fold 

 of this stage ; and the differences in this respect, seen in Figs. S and 9, is 

 not to be accounted for by the difference in age. The arching of the dorsal 

 fold at the time of hatching is not often so pronounced as in Fig. 8, and 

 is frequently less than in Fig. 9, which represents a stage of thirty-six hours. 

 The round, fleshy pectorals are now quite prominent. The yolk-sac is 

 very large, and broadly ovate in form. The dimensions of this stage are 

 as follows: — 



Length 2.70 .mm. 



Yolk-sac 92 X -05 " 



Yolk-sac to vent . . . . . . . . . .15 " 



Vent to tip 1.50 " 



Width of head 40 " 



Width of body (at level of vent) 17 " 



The three remaining stages (Figs. 10-12) were captured by surface 

 skimming, and their age is therefore unknown. The principal changes con- 

 sist in the disappearance of the yolk-sac, the prolongation of the snout, with 

 the lower jaw far in advance of the upper, the appearance of two thickenings 

 in the embryonic fold for the dorsal fins, the diminished breadth of the fold, 

 especially in the posterior half, the presence of large pectorals, bluish green 

 pigment in the eyes, and the more highly developed state of the black chro- 

 matophores, now represented by numerous radiating dendritic cells scattered 

 over the sides. 



The eggs of this species are found through the summer months, but 

 never in very large numbers. 



THE BLUE-FISH. 



Temnodon saltator, Lin. (Pomatomus saltatrix, Gill.) 



Plates IV. and V. Figs. 1-15. 



Nothing definite is known in regard to the breeding habits of the Blue- 

 fish, and no description of the eggs has been given. The egg here figured 

 is easily distinguished from other pelagic fish eggs by the partial segmenta- 

 tion of the yolk ; and it is quite probable that an examination of ripe eggs 

 obtained from the fish would clear up the uncertainty in respect to the spe- 

 cies to which it belongs. We have found these eggs from the middle of 

 June to (be middle of August, but never more than a few at a time. It is 

 most abundant about the middle and latter part of July. As a rule, the egg 



