276 PEOCEEDINGS OF THE AMERICAN ACADEMY 



extending from the top of the head to the end of posterior dorsal 

 along upper side of stomach and base of anal and caudal. Eye 

 bright blue, bluish silvery body with a few faint pigment cells uni- 

 formly scattered over the flanks. The Carangidas with rudimentary 

 ventrals and no anterior dorsals are evidently genera representing the 

 embryonic stages of this family. 



Stromateus tkiacanthus, Pec^ (Por,onotus tri acanthus, Gill). 

 (Plate VI.) 



The more advanced stages of the Butterfish (from 10-20™'° in 

 length and larger) are frequently found within the tentacles of our 

 common Dactylometra. The younger stages were, however, all fished 

 up from the surface with the hand-net. 



The youngest stage of Poronotus observed measured 7"" in length 

 (Plate VI. fig. 1). The body in this stage is comparatively stout, 

 the head large. The caudal is already developing, though the em- 

 bryonic lobe is still present ; the urostyle is quite large. The dorsal 

 and anal embryonic fins are narrow. The pectoral is large, rounded, 

 transparent, the permanent rays well developed. The eye is large, 

 and has the peculiar greenish-brown metallic lustre of the adult; 

 this makes it comparatively easy to recognize the embryo Butterfish 

 in the early stages. 



There is a line of large chromatophores along the base of the anal, 

 extending from the vent along the ventral line to the operculum, a few 

 large pigment cells (four to five) on the digestive cavity, and a large 

 patch over the swimming bladder. There are four comparatively small 

 pigment cells along the lateral line, three to four along the dorsal 

 line behind the head, and eight to ten irregular pigment spots on the 

 head above the eye, with three or four small pigment cells in advance 

 of the eye and on the jaws. In the following stage (Plate VI. fig. 2) 

 the anterior part of the body and the head have a light brownish tint, 

 the tail fin is nearly symmetrical, it has permanent fin rays with three 

 articulations, the body is somewhat more elongated, there are the first 

 traces of the permanent dorsal and anal fin rays along the dorsal and 

 ventral lines. The general distribution of the pigment spots is very 

 similar to that of the previous stages ; the cells are, however, some- 

 what more dendritic. In the following stage figured (Plate VI. fig. 3) 

 the chromatophores have greatly increased in number and size, espe- 

 cially on the upper part of the head and along the flanks of the ante- 



