54 THE PELAGIC STAGES OF YOUNG FISHES. 



Fig. 3. Just before hatching (forty-two hours after Fig. 1). X 55. 



Fig. 4. A somewhat younger stage than Fig 2, showing two oil-globules. 



Fig. 5. Same, somewhat later, after coalescence of the globules. 



Fig. 6. Profile view at time of hatching. X 55. 



Fig. 7. Similar view of another individual, showing the lateral-line organs and the lateral nerve. X 55. 



Fig. 8. Seen from the dorsal side, showing lateral-line organs of both sides. 



Fig. 9. Twenty-four to thirty-six hours old. 



Fig. 10. Frontal view of a specimen twelve hours old. 



Fig. 11. Profile view of the same. 



Fig. 12. Twelve days old (oldest raised from the egg). 



Fig. 13. A later pelagic stage. Embryonic fold much reduced. 



Fig. 14. Still more advanced pelagic stage. 



Fig. 15. The oldest pelagic stage. 



PLATES XIY. and XV. 

 Pseudorhombus oblougus, Stoker (l'l. XXXI. Fig. 3). 



Fig. 1. An egg al the time the blastopore closes, before any pigment has appeared in the chromatoblasts. 

 Fig. 2. A little later stage, in which Kupffer's vesicle is disappearing. Chromatoblasts still colorless. 

 Fig. 3. Minute round black pigment-dots have now appeared in some of the chromatoblasts. Yellow 



pigment just begins to appear on the body. 

 Fig. i. Somewhat later; the yellow pigment, now more pronounced, has the form of round cells in the 

 region of the tail, but appears in diffuse yellow stains farther forward. 

 Just before hatching. Yellow pigment less abundant than in most eggs of this stage. 

 Young Flounder, twelve hours old. Yellow pigment has become reddish brown on the embryonic 

 fold, and concentrated into patches; that of the body is evenly diffused. The black cells are 

 dendritic and unusually prominent. 

 Thirty-six hours old. Both black and yellow pigment-cells are in a state of semi-expansion. 

 Sixty hours old. Gives the more typical arrangement of the yellow patches, here dusky buff. 

 A dorsal view of the head at the same age, showing that it is still symmetrical. 

 About three days and a half old. This specimen and I hat of Fig. 8 were taken at Nahant. 

 Sixty hours old. 



Somewhat older stage than Fig. 11. The black spots are more closely packed along the lower side 

 of the axis, with more numerous dendritic spokes. The single patch of black spots half-way 

 between the vent and the extremity of the tail fin very marked. 

 Fig. 13. Still older stage than Fig. 12. The right eye is no longer symmetrically placed; the black spots, 

 with the exception of the caudal patch, are arranged in a close line along the lower side of the 

 muscular axis, the upper part of the anterior portion of the chorda, and the lower edge of the 

 stomach. 

 Fig. 11. Slightly older stage than Fig. 13. The chromatophorcs arc contracted to mere dots, while they are 

 fully expanded in the preceding stage. The embryonic fins of the last two stages nave become 

 comparatively narrower. The yellow spots now form two large patches, one along the upper part 

 of the stomach, the other over the caudal patch. 



PLATE XVI. 

 Pleuronectes americanus, Walb. 



Fig. 1. An exceptionally small egg (.70 X -73 mm.) doubtfully classed with the following stages. The 

 figure shows the embryo shortly alter the closure of the blastopore, and represents one of the 

 earliest stages in the development of the chromatophores. X 55. 



Fig. 2 A somewhai younger stage, in which the blastopore has just closed, showing the first appearance 

 of pigment-dots. 



Fig. 3. A later stage, in which the pigment is more perfectly developed. 



