DEVELOPMENT AND LIFE-HISTORIES OF TELEOSTEAN FISHES. 849 



diameter the ovum measures # 045 inch. The large oil-globules have a diameter of '0015 

 inch, while the smaller measure "0004 inch in diameter. The capsule, in a few slightly 

 undulated, is somewhat thick and tough, so that considerable force is necessary to rupture 

 it. The zona is very distinctly punctate, even more so than in that of the plaice 

 (PI. I. fig. 20). In one example the surface of the zona was covered with flattened 

 papillae, giving it a scabrous aspect (PI. X. fig. 7). In the early condition of the blasto- 

 derm the border of the yolk under it presented a few large vesicles (PL XXII. fig. l), 

 which projected beyond the edge of the periblast, and at a later stage this vesicular 

 condition extended round the greater part of the yolk, except just at the tail of the 

 embryo. Moreover, pigment rapidly develops over the surface of the yolk as well as 

 on the head of the embryo, and it has a dull whitish or faintly yellowish hue, in marked 

 contrast to the yellow tint of the gurnard. 



When the embryo is fairly formed' (PI. II. fig. 11), the groups of oil-globules change 

 their position, most occurring along the ventral surface of the embryo, as in the egg of a 

 Solea (?) described by Raffaele (No. 125a, p. 42, Taf. 1, figs. 33 and 34). # 



The oil-globules in this egg comport themselves differently from the single globule in 

 other eggs, e.g., of the gurnard. They do not move freely, so far as observed, at any 

 period of development, but retain their positions during the motions of the ovum. Their 

 relation to the periblast must therefore differ materially from that in the gurnard already 

 described. Raffaele considers they are in the cortical protoplasm, 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, the probability that something like a streaming of the protoplasm of 

 the periblast takes place about the period of the closure of the blastopore, so as to carry 

 the globules under the developing embryo. 



While in the living egg the foregoing is the condition so far as can be observed, it is 

 otherwise in the dead egg after the lapse of a day or two. In a dead egg at the morula- 

 stage, the oil-globules (now somewhat larger and of a dull yellowish colour) had grouped 

 themselves at the upper pole, the disc being at the lower. When the disc was placed 

 uppermost the oil-globules moved up to it at first apparently on the surface of the yolk, 

 but a more minute examination showed that they also moved through the yolk. It is 

 clear, therefore, that a change had occurred in the protoplasmic investment of the yolk so 

 as to release the oil-globules, which to some extent had coalesced, and permit them to 

 pass through it. 



The eggs develop with moderate rapidity, so that those with the rim about a third 

 over, and which presented segments in the periblast under the blastoderm (forming the 

 vesicular condition), hatched on the fourth day thereafter. The larval sole is a character- 

 istic form (PI. XVII. fig. 13), the entire body, yolk-sac, and marginal fin being minutely 



* Mr Cunningham, in Ms recent paper, describes the oil-globules as aggregated on each side of the embryo, though 

 there are a few groups at other parts of the surface of the yolk. He figures other stages than those given in this 

 paper, and shows the vesicular condition at a different period from that in our fig. 1, PI. XXII. 



VOL. XXXV. PART III. (NO. 19). 6 Q 



