112 
SPOLIA ZEYLANICA. 
the hind-body. The blood in at least the hinder moiety of the 
posterior cardinal vein flows backwards into the subintestinal vein 
in conjunction with the caudal circulation—a fact which I have 
repeatedly observed in other fish larvae as well as in “ lula. ” 
For three days after hatching the larvae remain at the surface of 
the water, resting on one side with the yolk-sac up. When they 
swim they sway and rotate irregularly, sometimes apparently 
spinning round. The network of stellate cells over the yolk-sac 
soon darkens and forms a pigment reticulum, and pigment begins to 
appear in the eyes on the first day, but, as I have already mentioned, 
at the time of hatching the eyes are clear and devoid of pigment. 
In fact, throughout a great part of the first day after hatching, the 
spawn presents the same appearance as it did before hatching, and 
only closer inspection reveals that the yolk-laden larvae have 
escaped from the egg-membranes. First day hatchlings are thus 
distinguished as unpigmented or clear “ lula” surface hatchlings. 
Second and third day hatchlings are called pigmented “ lula ” 
' surface hatchlings. They measure 4 * 5 mm. in length. Whereas in 
the very young hatchling the caudal vein passes in toto alongside the 
hind-gut into the subintestinal system (Fig. 6), it is now seen to 
give rise to a capillary system which is joined by the posterior 
cardinal vein and discharges into the subintestinal vein behind 
and below the yolk-sac (Fig. 7). Connected with this and with the 
anterior vessel shown in Fig. 6 there is a marvellous yolk-sac circula¬ 
tion, forming a perfect system of capillary irrigation. During the 
early days of larval life, neither the aorta nor the caudal vein extends 
backwards as far as the end of the notochord, but the former opens 
directly into the latter behind the free end of the septum, which 
otherwise separates the two vessels at this stage ; and the point of 
confluence lies some distance in front of the end of the notochord. 
About the twelfth day after hatching the vessels are carried farther 
backwards, and a capillary network forms in the caudal fin beyond 
and below the tip of the notochord (PI. III., Fig. 11). Larvse 
of the second day no longer have the clear eyes of the first day, 
for the eyes now contain black pigment. Another striking new 
character of this stage is the first appearance of the pectoral fins 
as rudimentary buds in situ above the yolk-sac. 
By the third day the length is slightly increased, about 5 mm., 
the pigmentation is intensified, and the mouth is open. Besides 
the uniform layer of pigment over the yolk-sac, stellate cells are 
distributed over the myotomes, especially along their upper and 
lower borders, and a thin fine of cells occurs along the centre of the 
dorsal and ventral embryonic fins, which at this stage show an equal 
amount of pigment. On this day indications of the air-sac appear, 
the pectoral fins begin to flap, and respiratory movements commence. 
The larvse still rest at the surface when not swimming, and are 
incapable of resting at the bottom. 
