292 PROCEEDINGS OP THE AMERICAN ACADEMY 



caudal embryonic lobe by a deep narrow slit, and in both these fins, as 

 well as the caudal, the permanent rays have begun to be formed, being 

 most advanced in the caudal fins. There are two gigantic black chro- 

 matophores extending over the dorsal part of the stomach, three 

 prominent chromatophores of the same color in the posterior flanks of 

 the body immediately in the line of separation of the dorsal and anal 

 from the caudal lobe, and the remnant of a small black pigment patch 

 at the base of the caudal rays. On the top of the cerebrum there is 

 a patch of black pigment, and also on the anterior part of the dorsal 

 line near the base of the brain. The general color of the young fish 

 at this stage is yellowish, with brilliant yellow patches surrounding the 

 dark patches of black chromatophores ; the eye is of a dull blue color, 

 with a black band above the pupil. In the next stage (Plate XIY. 

 fig. 3), measuring 6.5""^ in length, the caudal fin has lost its ganoid 

 lobe and has become symmetrical ; the cleft separating the dorsal and 

 anal from the caudal lobe has completely isolated them from the 

 caudal ; the snout has lengthened somewhat, the pectorals and ventrals 

 have become larger. The principal difference in the appearance of 

 these two stages consists in the great development of closely packed 

 chromatophores, which cover uniformly the whole body and the pos- 

 terior part of the head. The fins alone are as yet free from them ; but 

 at the base of the dorsal and anal there is a prominent continuous 

 line of black pigment cells, and a few small inconspicuous chromato- 

 phores at the base of the caudal rays. The next stage (Plate XIV. 

 fig. 4), but slightly older than Plate XIV. fig. 3, measuring 7'"'° in 

 length, differs from it mainly in the absence of the coating of chro- 

 matophores. There are, as appears from this stage (Plate XIV. 

 fig. 4), from that of Plate XIV. fig. 3, and from the subsequent stage 

 figured, three sets of coloring characterized by the extremes here 

 figured. One as in the stage of Plate XIV. fig. 3, with densely packed 

 dendritic chromatophores ; the other, fig. 4, with only a few prominent 

 patches of large chromatophores, and the intermediate stage (Plate 

 XIV. fig. 5), measuring 11'^'^ in length, in which we have the large 

 prominent patches (Plate XIV. fig. 5), with the band of continuous 

 pigment cells along the base of the dorsal and anal, and the body uni- 

 formly covered with comparatively small pigment spots. This will 

 probably account for the great differences already noticed in the 

 youngest stages (Plate XIIL figs. 4, 5, 6, and Plate XIII. 1, 2, 3) 

 in the presence or absence and distribution of the dendritic chro- 

 matophores. We might naturally expect such a difference from the 



