St. Andrews Marine Laboratory. 195 



are very hardy, and could readily be reared in suitable 

 enclosures. 



4. On the Ova and Larvoi of Arnoglossus megastoma. 



The ova were procured from the fishing-grounds off 

 Aberdeen in May, and, as Raffaele pointed out, possess a 

 single oil-globule. They have a diameter of 1'1430 millim., 

 and the oil-globule '3048 millim. All are remarkably 

 buoyant, and at an early stage of development possess a 

 perivitelline space. The zona is distinguished by having 

 elevated lines or ridges with very fine strise between them, 

 as in the brill and lemon-dab, and these ridges remain after 

 hatching has taken place. The micropyle is sometimes 

 situated in the centre of a radiate series of lines in a space 

 bounded by other ridges. Development is comparatively 

 rapid, so that on the fourth day the perivitelline space has 

 considerably increased — from the diminution of the yolk, the 

 tail of the embryo projects as far as the oil-globule, and its 

 black chromatophores have commenced to ramify. The 

 chromatophores under the oil-globule are minutely branched. 

 The otocysts are formed, and faint pulsations of the heart are 

 present. Some were hatched on the fifth day. 



The larva possesses only black pigment somewhat uniformly 

 scattered over the body, with a few specks on the head. They 

 also occur both dorsally and ventrally in the marginal fin, 

 and are V-shaped in the latter. The large oil-globule lies at 

 the posterior and inferior part of the yolk, and in lateral views 

 is somewhat elliptical. The notochord is multicolumnar. 

 The solid strand of the rectum comes to the edge of the 

 marginal fin, and a preanal portion of this fin occurs between 

 it and the yolk. Two days afterwards a yellow pigment 

 appeared amongst the black on the marginal fin and along the 

 sides of the body posteriorly, but in some specimens, which were 

 probably more normal in their emergence, yellow pigment 

 was noticeable on the caudal region. The black pigment in 

 the eyes Avas late in developing (fifth to sixth day). The 

 mouth opens early, but the mandibular cartilages are less 

 developed than in the gadoids, yet the aperture is proportion- 

 ally large and the movements extensive. The canary-yellow 

 pigment was conspicuous in the posterior part of the body in 

 the oldest examples. 



Briefly, then, the larva is recognized by the characteristic 

 black chromatophores of the marginal fin dorsally and 

 ventrally, the slightly elliptical outline of the oil-globule in 

 lateral view, the pre-anal marginal fin, and the shape of the 

 head. 



