OF ARTS AND SCIENCES. 281 



the head loses in later stages the comparatively huge size which char- 

 acterizes nearly all the younger stages of bony Fishes soon after they 

 leave the egg. 



The yolk bag of the young Lophius when just hatched is compara- 

 tively small (Plate XVI. fig. 4), being almost entirely absorbed while 

 still in the egg, and it soon disappears entirely (Plate XVI. fig. 5). 

 In a somewhat younger stage, taken out of the egg (Plate XVI. 

 fig. 3), it is quite globular, and the first trace of the pectorals and of 

 the ventrals as a mere fold of the embryonic fin fold, which extends 

 over the yolk bag, is still well shown. 



In these earlier stages (Plate XVI. fig. 3, and Plate XVI. fig. 1) 

 the embryonic fin folds are covered with minute round black pig- 

 ment spots. It is only in much more advanced stages (Plate XVIII. 

 fig. 1) that we begin to find traces of the ordinary dendritic pigment 

 spots which eventually cover the dorsal, anal, and caudal fins (Plate 

 XVIII. fig. 2). 



The young a few days after hatching (Plate XVI. fig. 5) differ 

 from the preceding stage mainly in the greater elongation of the 

 head, the disappearance of the yolk bag, the comparatively larger 

 pectorals, and in the position of the eye, which is somewhat higher. 

 In the next stages (Plate XVII. figs. 1-3) the head has become still 

 more elongated, the lower jaw projects well beyond the upper jaw, 

 the branchiae are well developed, the eye has assumed a still higher 

 position in the head, the pectorals have greatly increased in size, the 

 single anterior dorsal element is more than double what it was in the 

 size figured before, and the ventrals have become greatly lengthened, 

 showing a trace of the second ray at the base of the larger ones. 

 The alimentary canal is well circumscribed, and the pigment spots 

 over the remainder of the yolk bag, the top of the brain, and the 

 base of the chorda are of an intense black, with a slight tinge of 

 yellow over the alimentary canal. 



The outline of the body has somewhat lengthened, the embryonic 

 dorsal and ventral fins remain of great width, showing as yet no trace 

 of separation of an anal or dorsal or caudal fin, beyond the presence 

 of embryonic fin rays in the large caudal pigment spot (Plate XVII. 

 fig. 3), already present in younger stages. 



In somewhat older stages the original dorsal ray shows a trace of 

 a second ray behind its base (Plate XVII. fig. 4), which in a still 

 older stage attains half the length of the original ray (Plate XVII. 

 fig. 5.). The second ray of the pectorals of this same stage (Plate 



