34 THE PELAGIC STAGES OF YOUNG FISHES. 



one ventral, are seen nearer the end of the tail. In Fig. 7 (36 hours) the first 

 three blotches are represented by a continuous streak, and the same is true 

 of the next two on the dorsal fold, as well as of the three on the ventral 

 fold. A similar concentration, carried still further, is seen in Fig. 10 (about 

 84 hours), where the first three blotches are wanting. In Figs. 11 (60 hours) 

 and 12, these spots are still distinct, while in Figs. 13 and 14 thej' are reduced 

 to two. In the course of the third day a blue pigment appears in the eye 

 (Fig. 11), which characterizes the remaining stages here figured. 



The granular cells, seen on the tail of Fig. 7, extend over the entire 

 surface, and are present in the later stages, becoming somewhat larger and 

 more opaque as the fish grows older. 



This fish is comparatively long at the time of hatching, and the embry- 

 onic fin-fold is narrow, seldom arching as in Figs. 7 and 11. The vent is 

 marginal from the first, and is placed a little in front of the middle. 



Pleuronectes americanus, Walb. (Platessa plana, Stoker.) 



Plate XVI. Figs. l-lO. 



One of the most common eggs found at Newport in July and August is 

 that referred by Mr. Agassiz to the above species of Flounder. The stages 

 connecting this egg with P. americanus, the later stages of which are de- 

 scribed in "The Young Stages of Osseous Fishes," * were only satisfactorily 

 identified during the early part of July, 1884; and this explains our in- 

 ability to assign more precise limits to the period of occurrence. This egg 

 resembles in many respects that of Ctenolabrus, and was confounded with 

 it to the date above given. There is little doubt that the egg occurs 

 during a large part of June, and perhaps as early as May. 



The average size of the eo-o- is a little over .80 mm. ; but it varies consid- 

 erably, ranging between .78 mm. and .90 mm. The egg is perfectly trans- 

 parent and colorless, and has no oil-globule. A much smaller egg (.70 mm. 

 or less), presenting in other respects identical characters with this species, 

 was occasionally found (Fig. 1). We were unable to obtain many stages of 

 this small egg, and must therefore leave the question of its identity unsettled. 



The pigment makes its appearance about the time the blastopore closes, 

 in the form of small rounded black dots (.00-") mm. in diameter), arranged in 



* Agassiz, Alexander. " Development of the Flounders," True. Amer Acad. Arts and Sciences, XIV, 

 riat.es III., IV., and V . 1878. 



