DEVELOPMENT AND LIFE-HISTORIES OF TELEOSTEAN FISHES. 807 
and the epidermis of the cephalic region is very uneven. The heart (4) has the siphonal 
shape, and the dilated venous end is curved to the right. In some examples a large 
space—RyDEr's segmentation-cavity—is present below and in front of the heart (PI. VIIL. 
fig. 6, pd), while in others this space is either much reduced or is not present. In some, 
again, the pigment is less developed than in others, the former possibly having emerged 
at an earlier stage than the latter. The larva at this time hangs in the water with 
the yolk uppermost, the head being often directed downward. 
2nd day.—On the second day the pericardial wall has, in front, shifted downward, so 
that its attachment terminates anteriorly some distance below the junction of the throat 
and the yolk-sac. The latter is diminishing, and has already receded from the rectal 
bend of the intestine. A large lumen is present in the oesophagus, and it distinetly 
passes beneath the eye. ‘The pigment-corpuscles at the margin of the dorsal fin, which 
were at first amorphous, are now finely branched. A very remarkable phenomenon is 
the shortening of the region between the pectorals and the otocysts, coincident with the 
great growth of the pectoral fins. Three branchial arches are distinctly visible, and 
have an oblique dorso-ventral direction, but the slits do not appear to open externally 
at this stage. 
3rd day.—On the third day (Pl. XIV. fig. 2) the chief changes are the increased 
prominence of the snout, which now projects in front of the yolk-sac, the general 
shrinking of the latter, and the very finely branched condition of the pigment-corpuscles 
in the marginal fin, pectorals, and on the yolk-sac (PI. V. fig. 2a). More pigment, of 
a yellowish colour, now occurs over the mid-brain and round the eye. The reticulation 
of the peculiar pigment-corpuscles of the yolk-sac is conspicuous (PI. V. fig. 2a), these 
bodies wholly differing in shape from those of the embryonic fin and other parts (PI. 
XVI. fig. 8, those of the trunk being figured on Pl. V. fig. 2). The pectoral fin has 
acquired greater prominence, and its distal margin is rounded. Little change has 
occurred in the outline of the marginal fin. Surface-views still show that the oral 
region is impervious from the widely open mouth to the eye, but the lumen of the 
alimentary canal posteriorly is very distinct. The liver projects prominently opposite 
the posterior border of the pectoral fin. The urinary vesicle (wv) is elongated from above 
downward, and the segmental ducts often appear to enlarge before opening into it. The 
larve at this time show increased activity, and jerk or dart about at intervals, 
apparently for respiratory purposes. In certain cases the well formed and active 
larvee keep near the bottom of the vessel, while the deformed examples float helplessly 
on the surface. They occasionally remain still, hanging obliquely with the head down- 
ward, and gradually descend to rest quietly on the bottom. The fine yellow pigment and 
shining oil-globule in the yolk are diagnostic features. The dead sometimes float as 
minute white objects on the surface, though generally they sink to the bottom. 
5th day.—When five days old the gurnard measures *165 of an inch. The eyes 
have a greenish lustre, with black pigment. The ochre-yellow pigment is now chiefly 
confined to the head, yolk-sac—where the corpuscles are finely ramose, the pectorals, the 
