FISH-CULTURAL INVESTIGATIONS AT ST. ANDREWS, SCOTLAND 253 



differs materially from thai of A. megastoma, both in structure and coloration; and it is 

 unknown whether the careful Italian author refers to A. laterna or another form. He- 

 represents the post-larv al Arnoglossus, again, with a long ray like a flagellum anteriorly. 



Mr. Holt*, who found ripe forms of both series in March, April, and May, states 

 that the eggs arc very translucent, have a diameter of 1-08 to 1-13, and possess a 

 single oil-globule, -30 mm. in diameter. He thinks, from his observations off the west 

 const of Ireland, that spawning takes place only in moderately deep water, and neces- 

 sarily therefore at some distance from shore, always at a great distance from the coast 

 when the declivity is very gradual. On the eastern shores of Scotland the species is 

 an inhabitant of the deeper water. 



Three series of ova reached the laboratory in May, 1892, but it will be sufficient to 

 allude only to the last, which were at an early stage of development on the 28th of 

 May at 11 a. in. They had a diameter of 1-1430 mm., while the oil-globule measured 

 •3048 mm. All the living eggs were remarkably buoyant and had a perivitelliue 

 space. The zona radiata conforms to the type seen in the brill and lemon-dab, being 

 covered with raised lines or ridges with very tine stria' between them. The usual 

 minute punctures densely covef the surface. The micropyle is difficult to distinguish, 

 but it appears to be sometimes situated in the center of a radial series of lines in a 

 space bounded by other ridges. It is best seen by setting several eggs together in a 

 cell, so that they support each other and give special positions unattainable when 

 each is free. • 



On the 20th May (next day) the rim had either reached the equator or extended 

 beyond it, and a, dimple was often present on each side (in optical section) where the 

 rim constricted the yolk. The following day (30th May) the embryo was fully half 

 round the yolk and the perivitelliue space had increased. The lenses are now present, 

 and black chroinatophores appear under the oil-globule and in the caudal region. 



Further changes before hatching were the increase in the perivitelliue space from 

 the diminution of the yolk, the ramifications of the chroinatophores under the oil- 

 globule and on the tail. Black pigment also appeared along the sides of the embryo. 

 Larva 1 , were hatched on the 1st June, perhaps prematurely. They possess only black 

 pigment, which is somewhat uniformly scattered over the body with a few specks on 

 the head, and it also occurs both dorsally and ventrally in the marginal fin. Thus 

 five or six V-shaped chroinatophores are found near the margin of the dorsal fin 

 behind the yolk-sac — almost intermediate between it and the tip of the tail, and two 

 similar or somewhat triangular ones opposite the former ventrally. The large oil- 

 globule lies at the posterior and inferior part of the yolk. The otocysts are simple 

 sacs. No pigment exists in the eyes. The notochord is multicolumnar. The solid 

 strand of the rectum comes to the edge of the marginal fin, and a pre-aual portion of 

 this fin is present. The urinary vesicle shows only a small central chamber. The 

 oil- globule in lateral views is somewhat elliptical. 



Two days afterward (June 3) yellow pigment was apparent amongst the black in 

 the marginal fin, and along the sides of the body posteriorly. The yolk-sac, as a rule, 

 has no chroinatophores, one or two only occasionally being situated at the upper part 

 of the region. The enlargement of the otocysts, liver, and other organs is considerable, 

 and the skin is minutely vesicular. In larva; which only escaped at this date (June 3) 

 the yellow pigment was not noticeable on the caudal region. 



* Report of Council, Roy. Dub. Soc, 1891, p. 238. 



