246 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



to be comparatively large. Thus in a specimen with the tail slightly shortened (by 

 curvature) the total length was 2-4 mm., while the yolk-sac from its anterior to its 

 posterior border was 1*2 mm. 



Five days after hatching stellate black chromatophores appear on the yolk-sac 

 and along the sides of the body, ouly terminating near the tip of the tail. The yellow 

 chromatophores are also more evident on the yolk-sac. The otocyst shows a double 

 border. The position of the rectum is almost unchanged. The yolk-sac soon dimin- 

 ishes and the growth of the branchial arches, gill-slits, pectorals, and other parts is 

 apparent, while the mouth opens. 



Two days later the yolk in some had quite disappeared, and the mouth is widely 

 open, though the mandible is as a rule rigid. The pectorals are large fan-shaped 

 blades and are carried upward. Even before the yolk has been absorbed the larvae 

 swim on edge, resting afterwards on the side. The eyes are silvery on the bottom by 

 reflected light, but have a gorgeous bronzed hue by transmitted light. In the older 

 examples the yellow pigment seems to be less conspicuous, for it is present only on the 

 head and anterior region, with a few specks on the pectorals. The increase of the 

 black pigment over the abdomen is noticeable. The circulation of the colorless blood 

 is visible in the dorsal aorta and the cardinal veins. The swim-bladder is well marked. 

 They constantly dart about with open mouth, seldom resting more than a second or 

 two, so that delineation is difficult. 



At a slightly later stage the yellowish pigment had disappeared except from the 

 cheeks, and the pectorals had increased in size. The marginal fin became vesicular ; 

 indeed the specimens were comparatively delicate, often perishing if placed in water 

 on a slide. A few survived till the 24th June without presenting any noteworthy 

 change except the appearance of a dorsal and a ventral skeletal bar representing the 

 shoulder girdle. 



ON A PECULIAR EXAMPLE (HYBRID?) OF THE POOR COD (GADUS MINUTUS). 



A fisherman procured by a hook on the 24th March a fish which he and others 

 supposed to be a hybrid between the whiting and the bib, or between the former and 

 the poor cod, and he sent it to the laboratory. 



The extreme length of the specimen was Ih inches, and the greatest depth 1£ 

 inches. In general outline it somewhat approached the whiting, though the dusky 

 bronzed pigment of the dorsum and dorsolateral regions, the somewhat coarser scales, 

 together with the shape of the head, the presence of a barbule, aud the condition of 

 the pelvic fins leaned to the poor cod. Yet it distinctly differed from the latter in 

 general aspect, and in the much more silvery infero -lateral regions aud abdomen. 



In regard to the shape of the body and the course of the lateral line it most nearly 

 approached the poor cod, though it was more elongated. Moreover, the curve of 

 the lateral line kept at a nearly uniform height, or even with a tendency upward 

 till beyond the tip of the pectoral, and the downward curve was decidedly more 

 abrupt. It differed in this respect not only from the poor cod, but from the whiting 

 and the bib. This curvature may be related to the marked depression in the dorsal 

 outline from the posterior border of the first dorsal tin to the middle of the second, 

 but it is not connected with any abnormality of the vertebral column. 



The fins agreed more or less with those of the whiting, the first dorsal espe- 

 cially differing from that in the poor cod and bib, and corresponding rather with that 



