146 



side to the heart. Another efferent vessel may be seen, though 

 less distinctly, proceeding along the body to the caudal region, 

 where it apparently joins the afferent vessel first mentioned. 

 On the day following, the pectoral fins were very distinctly 

 visible behind the lateral efferent vessels, and the day after that 

 the circulating system was much more developed, the whole sur- 

 face of the yolk showing a network of vessels through which the 

 blood corpuscles could be seen coursing rapidly. 



The embryo remained without much further change for fourteen 

 days. About two days before hatching a change was noted in the 

 pigment. The orbits become of a dark blue and a group of cells 

 of the same colour appears on the body near the pectoral fins, 

 which at this stage are about half the length of the head. In 

 addition to this, small blue specks appear along the whole 

 length of the body. Very little movement is observed in the 

 embryo before hatching, with the exception of the free pectoral 

 fin. (that not appressed against the egg capsule), which is in 

 almost constant motion. In the only case in which the actual 

 hatching was observed there was no rupture of the shell, but a 

 sort of scaling-off of part of the capsule. At the time of hatch- 

 ing, the embryo was about one and a quarter the circumference 

 of the egg. 



The newly-hatched larva (Plate X, fig. 54) is as much charac- 

 terised by the presence of distinctive colouring as it had been 

 previously by its absence. With the exception of the yolk and 

 fins, it is of a deep blue, which on examination with a low power 

 may be resolved into dark blue stellate cells, closely packed on 

 the dorsal aspect, but separated on the ventral region in front 

 cf the rectum and on a small part of the yolk adjacent to the 

 body (that part which at an early stage was characterised by 

 the presence of black stellate cells). The mouth is well deve- 

 loped and the lower jaw protrudes slightly beyond the upper. 

 The embryonic ventral fins are well developed ; that anterior to 

 the anus slightly overlaps the posterior one. The dorsal is not 

 so deep and begins further back, about half-way between the 

 tip of the snout and the end of the caudal rays. The rectum is 

 median, being about half-way between the posterior margin of 

 the yolk and the end of the body. 



The larva is long (one measured 8' 5 mm.), and swims with a 

 rather slow undulation of the whole body. 



After hatching, the absorption of the yolk proceeds at a rapid 

 rate, and three days later it has disappeared (Plate X, fig. 55). 

 A marked change has meanwhile occurred in the pigment. It 

 becomes differentiated into a dark blue band along the back, 

 extending on the side for about a third of the depth of the body. 

 The remainder of the body below this is of a silvery colour, 

 tmged with blue. At this stage, the rays of the caudal which 

 were present in the egg stage are more marked, but none have 

 as yet appeared in the other vertical fins. 



