THE FLOUNDER FAMILY. 389 



presented the condition shown in Plate IV, fig. 9, hatched 

 on the fourth day. When the embryo is formed pigment 

 develops rapidly on the head and on the surface of the yolk. 

 The tint is dull whitish or faintly yellowish, and thus in marked 

 contrast to the yellow of such species as the gurnard. 



When the embryo is fairly formed the groups of oil-globules 

 change their position, most occurring along the under-surface 

 of the developing fish, as in the egg of a sole described by 

 Raffaele. In connection with these oil-globules it may be 

 mentioned that they comport themselves differently from the 

 single globule in other eggs, such as those of the gurnard. 

 They do not move freely, as far as observed, at any period 

 of development, but retain their positions during the motions 

 of the ovum. Their relation to the protoplasmic covering 

 of the yolk must therefore differ materially from that in the 

 gurnard. Raffaele considers they are imbedded in that portion 

 of this layer which divides the vitelline segments, and move 

 with the latter. They certainly advance with the rim, but 

 their subsequent arrangement under the developing embryo is a 

 remarkable feature, indicating, indeed, besides concrescence, the 

 probability that something like a streaming of the protoplasm 

 of this layer takes place about the closure of the blastopore, so 

 as to carry the globules under the developing embryo. They 

 are, on the other hand, set free later in a dead egg, so that 

 they pass through the yolk as in the gurnard and other forms. 



The eggs of the sole are comparatively hardy, and the 

 larval sole is no less so. On its escape from the capsule 

 (Plate XVIII, fig. 2) it is about 3 mm. in length and the entire 

 body, yolk-sac, and marginal fin are minutely speckled with 

 opaque yellowish-white pigment. This is arranged in inter- 

 rupted touches on the body and marginal fin both dorsal ly and 

 ventrally behind the yolk-sac, so that the pleuronectid character 

 is early indicated. Moreover, the presence of pigment at the 

 extreme margin of the fin gives great apparent depth to the 

 body of the little fish. The yolk-sac is comparatively large 

 and globular, sustaining the animal readily in the water- 

 either in the inverted position or with the tail downward. At 

 first it progresses indifferently from the great size of the yolk, 



