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Part III. — Eleventh Annual Report 



(Plate VIII. Hg. 3) and the optic vesicles indicated. The lip of the 

 blastopore behind the embryo presented a peak or projection. 



Another series procured in the open sea olf Aberdeen by A. W. Brown, 

 the laboratory attendant, and received on the 10th June, were mostly 

 advanced. They ranged in size from -9525 mm. to *9906, so that they 

 were somewhat less than the previous examples, the largest being those 

 almost ready to hatch — indeed, some of the latter reached 1-0287 mm. in 

 diameter. The eyes of the advanced embryos are silvery (their con- 

 spicuous condition is one of the characteristic features of the egg), and 

 yellowish pigment is scattered over the head, body, and yolk. 



A few were hatched on the 11th June. The larval poor cod somewhat 

 resembles the whiting in coloration, and measures 2 - 3 to 2*4 mm. The 

 eyes are silvery-greenish, and the entire body and head are dappled with 

 minute yellow specks — invisible under a lens, but are seen by transmitted 

 light' under a low power of the microscope (Plate VIII. fig. 4). Black 

 chromatophores occur along the ventral border of the muscle-plates, the 

 tip of the tail alone being free. A less distinct series lies along the dorsal 

 edge, and a few r finely-branched specks occur on the head. The rectum 

 terminates blindly at the posterior and upper part of the yolk. The 

 latter seems to be comparatively large. Thus in a specimen with the tail 

 slightly shortened (curved) the total length was 2*4 mm., while the yolk-sac 

 from its anterior to its posterior border was 1*2 mm. (Plate VIII. fig. 5). 



Five days after hatching (that is, on the 15th June in the case of those 

 which escaped on the 11th), stellate black chromatophores appear on the 

 yolk-sac and along the sides of the body, only 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 has 

 altered little. 



On the 16th June considerable advancement had been made (Plate VIII. 

 fig. 6), though it was doubtful if the larvae belonged to the same series. 

 The increase in the ramifications of the stellate black pigment, the growth 

 of the branchial arches, gill-slits, pectorals, and other parts is apparent ; 

 while the yolk has diminished. A more advanced example had, indeed, 

 only a small portion of yolk, and the mouth was open, but the rectum had 

 not moved downward to any extent. The black pigment is chiefly 

 grouped along the abdominal roof and on the dorsal and ventral margins 

 of the muscle-plates. 



On the 18th June the yolk in some had quite disappeared. The mouth 

 is widely open, though the jaw is rigid, unless under occasional spasms. 

 The pectorals are large and fan-shaped, and are carried upwards. Even 

 before reaching this stage (i.e., before the yolk is quite absorbed) the 

 larvae swim on edge, resting afterwards on the bottom or the side. The 

 eyes are silvery by reflected light, but have a gorgeous bronzed hue by 

 transmitted. In the oldest examples the yellow colour seems to be less 

 conspicuous, for it is present only on the head and anterior region — with a 

 few specks on the pectorals, as represented in the specimen figured (Plate 

 VIII. fig. 7). The increase of the black pigment over the abdomen is note- 

 worthy. The circulation of the colourless blood is visible in the dorsal 

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

 young poor cod constantly darts about with open mouth, seldom resting 

 more than a second or two, so that it is difficult to delineate. 



At a slightly older stage (Plate VIII. fig. 8) the yellowish pigment had 

 disappeared except en the cheeks, and the pectorals had increased in size. 

 The marginal fin is slightly vesicular. They were comparatively delicate, 

 and often perished if placed in water on a slide. A few survived till the 

 24th June without presenting any change worthy of note, except the 

 appearance of a dorsal and ventral bar representing the shoulder-girdle. 



