DEVELOPMENT AND LIFE-HISTOKIES OF TELEOSTEAN FISHES. 807 



and the epidermis of the cephalic region is very uneven. The heart (h) 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. VIII. 

 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 distinctly 

 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 (PL 

 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 (uv) is elongated from above 

 downward, and the segmental ducts often appear to enlarge before opening into it. The 

 larvse 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 

 larvse 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. 



5 th 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 



