22 DEPARTMENT OF THE NATAL SERVICE 



6 GEORGE V, A. 1916 



has an eye -upon each side of the head like the cod, haddock, herring, and all "round" 

 fishes, and until it is 18 or 20 mm. (seven-tenths to eight-tenths inch) long shows little 

 indication of the tendency to the flattened form so characteristic of the later stages. 



The description which is here given refers mainly to the common species in the 

 Atlantic and North Pacific ocean, viz., Hippoglossus hippoglossus but the differences 

 between the two species in their young larval stages are not apparently very marked. 



The larval halibut, about half an inch long, is a long slender little fish, with a 

 snout slightly upturned and obtuse or flattened in front, quite unlike the flounder, 

 sole, and other pleuronectids. In most of these flat-fishes the snout is rounded and 

 curves downward, often with a sharp-hooked tip as in the sole (8olea vulgaris) ; but 

 the snout of the larval halibut is flattened in front, slightly upturned and " pig-like." 

 There is a marked depression between the eyes and the abrupt tip of the snout. The 

 minu.te spots of black pigment present in the youngest stage known, viz., 13-5 mm. 

 (•53 inch), are arranged in four indefinite rows along the caudal trunk behind the 

 anus, also a series along the dorsal line and along the ventral margin at the base of 

 the larval fin from the pectoral region posteriorly. On the larval fin membranes them- 

 selves scattered dots occur near the margin of the dorsal and ventral median fins. The 

 dots cease as these fins merge in the terminal tail fin. The upper and lower jaws are 

 very straight not curved as in some species and instead of bending downward, they 

 turn upward at an angle of about 60 degrees and the mandibular articulation projects 

 prominently in a characteristic manner. The eyes are large, silvery, and pigmented 

 in all stages knovsm, and the pectoral fins are well-developed. When about one-fifth 

 longer (PI. I. fig 2), very minute scattered spots of a reddish colour appear between the 

 myotomes or serial muscle masses of the body and give a faint reddish tinge to the 

 little fish when viewed by the naked eye. The large silvery eyes acquire a bright blue 

 tint and show very prominently. The next stage 22 to 23 mm. (-83 inch) long is 

 marked by the appearance of three groups of black spots or dark bands on the dorsal 

 iind ventral fins which are now supported by fin-rays, these rays being short and rudi- 

 mentary in the previous stage. The spots on the body assume the form of very distinct 

 wavy lines and the left eye begins to migrate from its position and is just visible as a 

 slight projection in the depression on the head (or rather forehead). The fish has now 

 a very characteristic halibut outline. 



When a length of an inch is reached (24^ mm.) PL I. fig. 5, the groups of spots in 

 transverse bands on the dorsal and anal median fins are more complex. Between the 

 four main stripes, three smaller bands appear, so that at least seven stripes or bands can 

 be counted upon each fin-expansion. This stage (PI. I. fig. 6) is reached before the 

 end of May, according to Dr. Schmidt, who obtained specimens on May 25 in water 

 of 116 metres (60 fathoms). 



' Nearly a month later a size of about 30 mm. (H inch) is reached, and the left 

 eye projects to the extent of about half of its mass above the contour of the forehead, 

 and the coloured bands (the broad and the narrower secondary bands) are a still more 

 marked feature on the dorsal and anal fins, while the spots on the side of the body 

 form four fairly distinct transverse bands (PI. I. fig. 7). On reaching a length of 

 34 mm. (PI. I. fig. 8) the fish still swims in the upright position, but the right side 

 is darker, more pigment being developed than on the left side of the fish. 

 The patches of colour lose somewhat the transverse arrangement and mingle 

 irregularly, producing a marbled pattern, which is very characteristic of the young 

 halibut for a considerable subsequent period. It is noteworthy that two roimded 

 patches appear near the base of the tail. Up to this stage the tail was transparent 

 and clear and free from any pigmentation. Dr. Schmidt obtained this stage on July 

 7 in a depth of 44 metres (24 fathoms). The next stage recorded is that of Dr. 

 Peterson, who secured an alleged halibut 51 mm. (2 inches) in length about the 

 end of May in water 500 fathoms in depth. He noted that it has seventy rays in the 

 anal fin, but the rays in the dorsal fin ar£ not recorded. When a length of 120 mm. 



