246 THE COD FAMILY. 



The egg of the haddock (Plate III, tigs. 1 and 2) is dis- 

 tinguished from that of the cod in its early stages only by the 

 difference in size (see Table). In the case of an egg fertilised 

 on the 20th of March, the embryo was hatched in twenty days. 

 On the fifth day there are indications of four or five vertebral 

 segments, and a few black pigment-spots appear on the sides 

 and back of the embryo. The blastopore closes on the llth day 

 and on the 12th there are indications of Kupffer's vesicle. By 

 this day an increase of the black pigment-spots has taken 

 place. These are large and star-shaped and are in great 

 abundance in the dorso-lateral region above the breast-fins. 



By the loth day, the embryo has increased considerably 

 both in length and in the size of the head-region, and by the 

 17th day, the heart beats about 30 to the minute, and embryonic 

 rays appear in the fins. The eyes then become black from 

 the presence of pigment, and the breast-fins have a distinct 



rim. 



On the 20th day, the larva emerges (Plate III, fig. 3). It is 

 then about '1 inch (3'5 to 4'1 mm.) in length. When the larva 

 is at rest, the buoyancy of the yolk-sac causes it to float 

 uppermost, but in its intermittent attempts at progression in 

 the comparatively still water it keeps itself in the normal 

 position. Black spots are aggregated behind the ears, and a 

 paired lateral row of the same pigment runs from the ab- 

 dominal region nearly to the tip of the tail. Over the surface 

 of the yolk is seen a delicate polygonal pattern or protoplasmic 

 net-work, which is also found in the flounder. 



The appearance of the larva on its escape is seen in Plate 

 IX, figs. 8 and 9. It has, in common with the cod, the charac- 

 teristic absence of all brightly coloured pigments, but can be 

 readily distinguished from the latter by the fact that the 

 disposition of the black pigment shows no tendency towards 

 transverse bands, which have been already emphasised in the 

 account of the development of the cod, though the general plan is 

 similar. The eyes in this figure show black dots in the iris and 

 are thus in an earlier stage than those of the cod. They are 

 often more pigmented than in this specimen, and Holt describes 

 newly hatched larval haddock with densely black eyes (west 



