438 Holt — On the Eggs and Larvce of Teleosteans. 



of Balfour. It is doubtful whether it really represents anything' more than an 

 unusually thick lamina of the zona.* The inner layer {st.), in which Brook noticed 

 no stratifications, is regarded by him as the zona-radiata ; and he remarks that the 

 two layers are occasionally separated by a space. I noticed an extreme opacity in 

 the capsule of an apparently healthy egg, which may, perhaps, be accounted for 

 by such a separation of the layers. 



Brook gives from twenty to thirty as the number of the oil globules, whereas, 

 I found only from eleven to nineteen in a considerable number which I counted, 

 whilst Raffaelef found only from four to ten in ova of 1'166 mm. which he 

 refers to this species, remarking that the slight discrepancy is probably due to 

 local variation. Brook makes no mention of any colouration of the globules, which 

 are distinctly yellowish (as in Raffaele's) or yellowish-green (fig. 31) in my 

 specimens, both eai'ly and advanced. I noticed one exception in which, at a very 

 early stage, the globules were colourless, but acquired an unusually pale yellowish 

 tint as development proceeded. As regards development, I have little to add to 

 Brook's excellent account. 



Pigment of a pale yellow colour (black by transmitted light) ajDpears in minute 

 round chromatophores in the embryo before the outgrowth of a free caudal region, 

 and spreads outwards from the sides over the yolk sac, the whole of which is 

 eventually studded with it (as in fig. 32). When the embryo possesses a free 

 caudal region equal to the rest of its length, the yellow chromatophores have 

 become larger and stellate, with a brilliant orange hue (brown by transmitted light); 

 they extend dorsally and ventrally along the free caudal region almost to its posterior 

 extremity, and along the gut on either side. Small black chromatophores (fig. 32) 

 have also appeared, following the course of the yellow pigment in the postanal 

 region, and distributed sparingly and somewhat irregularly over the anterior part 

 of the body. Stellate black chromatophores, much less abundant tlian the yellow, 

 occur on the yolk sac. Thus, at a comparatively late stage of development in ovo, 

 the yellow pigment is altogether in excess of the black, a condition which is 

 reversed in the older stages. The black chromatophores of the trunk become 

 stellate and increase greatly in size ; they appear on the brain, about the eye and 

 the large otocysts, on the base of the pectorals, and on the pelvic fins, whilst the 

 yellow pigmentation of the trunk appears to diminish. 



In the recently extruded larva (fig. 37), still mouthless and with comparatively 

 large yolk {y), the black pigment of the trunk forms a conspicuous line, dorsally 

 and ventrally, from the pelvic fins to the commencement of the posterior fourth of 



* Cf. M'lntosli and Prince, " On the Development and Life-Histories of the Teleostean Pood and other 

 Fishes," Trans. R. S. E., vol. xxxv., pt. iii. (No. 19), p. 671. 



■)■ " Le nova gallegianti e le larve dei Teleostei nel golfo di Napoli.," Mittheil. a. d. Zool. Stat, zu 

 Neapel., Bd. viii. 1, p. 30. 



