36 THE PELAGIC STAGES OF YOUNG FISHES. 



The yolk-sac has still the oblong elliptical form, and the granular aspect 

 of the eve, just appearing in the stage of Fig. 5, is now complete. 



Figs. 6 and 7 represent specimens somewhat older (about 30 hours); 

 the yolk-sac reduced in size. The transverse bars of black pigment seen 

 in Fig. 6 are unusual ; the more typical arrangement of pigment at this 

 stage is that given in Fig. 7. 



The eye begins to turn green at the age of thirty-six hours, growing 

 darker and assuming a coppery hue in later stages (Figs. 8 and 10). The 

 surface of the fish becomes granular as early as the stage of Fig. 6, and from 

 this time appears as represented in the middle and posterior portion of Fig. 9. 



The pectorals are quite transparent, and develop comparatively slowly 

 in these earlier stages (compare Plate XVI. figs. 7-10). 



Species No. 10. 



Plate XVII. Figs. 1-3. 



Only four eggs like that represented in Fig. 1 have been obtained, and 

 these were found in the early part of June, 1884. With one exception 

 (Lophius) this is the largest among the pelagic fish eggs occurring at New- 

 port. The egg measures 1.15 mm. and the oil-globule .28 mm. 



The entire outer surface of the body is clothed with a rich layer of black 

 dendritic chromatophores, only the fore part of the head and the end of the 

 tail being free from them. The same cells also thickly envelop the oil- 

 globule. A few clusters of bright yellow cells are characteristic of this 

 stage ; the largest and most conspicuous are two seen at the inner posterior 

 angles of the eyes. Two much smaller ones are placed on the ventral 

 surface near the base of the tail. Another small cluster is seen near the 

 middle of the body in this specimen, but it is not constant. At this time 

 may be seen on different parts of the yolk-sac a few peculiar unpigmented 

 cells, the nature and history of which were not ascertained. 



We did not succeed in hatching any one of these eggs, and their asso- 

 ciation with the stages seen in Figs. 2 and 3 is therefore purely a matter 

 of conjecture. 



Fig. 2 represents a young fish, which, from the size of the yolk-sac, must 

 be at least three or four days old. The black pigment now appears in the 

 form of large branching cells, of which two have a median dorsal position 

 above the mid-brain and oblongata, from four to six clasp the upper side 



