8 Fisher-y Board for Scotland. 



on the posterior lialf mauve pigment remains for some time. There is also very 

 ■considerable pigment on the yolk, the pigment spots being large, with dendritic 

 branches, and occurring in dense masses. There is one mass on the yolk under 

 the body, another mass over and encircling the oil-globule. The large dendritic 

 spots which cover the oil-globule give it a peculiar reticulated appearance, so that 

 the oil-drop, with its brilliance dimined, assumes a weak coffee colour. Isolated 

 dendritic pigment spots occur over the rest of the yolk. The eye is of a deep dark 

 blue colour. The mouth is closed, and there is no appearance of dorsal filaments 

 except that there is a slight depression in the embryonic fin above the head, the 

 edge of which is slightly thickened. 



The newly-hatched larva is, therefore, a striking object, and the large yolk, 

 pigmented body and short fleshy pigment-free tail, gives it a peculiar stumpy 

 appearance. 



Four days after hatching, the larva has gained considerably in size at the ex- 

 pense of the yolk, which has therefore diminished in volume. The increase in size 

 is most apparent in the yet pigment-free tail, which extends beyond the yolk to a 

 distance exceeding two diameters of the yolk. In the living state, the larva meas- 

 ures about 5 mm., while the yolk-sac has a diameter of about 2"3 mm. The yolk 

 has contracted considerably from the outer membrane. The head, as in the newly- 

 hatched larva, lies over the yolk in close proximity to it, and the contour of the 

 anterior ])ortion of the head is continuous with tliat of the yolk membrane, there 

 being a deep bay between the yolk and the head. The mouth is closed. In the 

 living condition, the head usually lies on the surface of the yolk. The pigment is 

 somewhat more intensively developed. The head, anterior portion of the body, 

 and gut, are covered with intense black pigment, whilst the eye is of a deep 

 black colour. The yolk, especially over the still large oil-globule, is also covered 

 with branching black pigment. The distinctive colour of the oil-globule has now 

 almost entirely disappeared, and is only seen below the dark-coloured pigment as 

 a faint coffee colour. The gut is covered with black pigment, especially in the region 

 of the pectoral fins, but this becomes less intensive towards the end of the food 

 canal. A short loop of the gut lies above the yolk-sac, and here, as well as in the 

 posterior j^ortion of the intestine, violet pigment may yet persist. The pectoral 

 fins, now somewhat large, are fleshy and scoop-shaped, and rounded or blunt at 

 the tip. The pelvic fins are much smaller and arise directly on the surface of the 

 yolk as conical prominences. Both the pectoral and pelvic fins are free from pig- 

 ment, and are of a dull mottled gray colour. 



The first dorsal fin-ray now appears beyond the margin of the embryonic fin. 

 In the newly-hatched larva, the first hint of the development of this ray was given 

 by the appearance of a thickening above the notochord just posterior to the pectoral 

 fin. This thickening, although ending rather abruptly in front, tails ofi posteriorly 

 in a wedge-shaped manner. Simultaneously, there appeared a depression in the 

 margin of the embryonic fin, the edges of which also become thickened. To the 

 naked eye, this bay in the embryonic fin looks like a constriction behind the head 

 of the larva. Soon there arises in the indentation of the embryonic fin a small 

 conical prominence, whilst the wedge-shaped thickening above the notochord 

 grows up to meet the indentation. This wedge-shaped thickening now extends 

 much further back on the top of the notochord, whilst there seems to be a shunting 

 forward of the whole mass. This may be more apparent than real, since, at this 

 period, the tail is growing at a relatively greater rate than the head region. The 

 tail has lost its distinctive rounded form, and is now somewhat pointed and appears 

 less fleshy. 



Larva — 7 to 8 days old. 



{Fig. 4). 



Considerable yolk remains even after the larva has been hatched a week. 

 Even now, the larva does not lose its unique position in the water, but floats 

 yolk uppermost, the body lying obliquely to the surface film. Occasionally, the 

 larva lies over to one side, but frequently there is vigorous movement from 

 side to side of the now much elongated tail. When a shght movement is given to 

 the water, the larva sinks a few inches, only to rise again slowly to the surface 



