St. Andreios Marine Laboratory. 55 



edge, which is not quite regular, from the occurrence of 

 minute projecting cells. The disk does not always occupy 

 the centre of the yolk under examination. Occasionally a 

 group of large oleaginous globules lies under tlie developing 

 disk, not at the uppermost pole of the q^^. 



On the 24th the embryo was outlined, with the optic 

 enlargements. The blastopore in some was almost closed, 

 and KupfFer's vesicle was represented by a few granules or 

 minute vesicles. The notochord formed a pale streak ex- 

 tending forward to the middle of the trunk, and the margins 

 of the body were faintly indicated. 



Next day the blastopore had closed and KupfFer's vesicle 

 was large. Numerous muscle-plates had formed and the 

 notochord could be traced forwards almost to the head. On 

 each side a delicate cellular border stretched backward outside 

 the muscle-plates. The granules had now disappeared from 

 the surface of the yolk. 



On the 26th March the embryo resembled Mr. Holt's 

 fig. 58, pi. vii. "^j and traces of blackish pigment appeared 

 along the body, best seen by placing white paper beneath the 

 specimens. Besides, there are in some the pale precursors of 

 the pigment-specks, which appear blackish by transmitted 

 light. The notochord was visible throughout, the lenses in 

 some were faintly indicated, and the otocysts appeared as 

 elongated thickenings with a longitudinal slit, as in the green 

 cod f. The heart was also distinct. The zona was thin and 

 readily ruptured, even when the Q^g was carefully lifted. 



The following day the blackish pigment formed dark bands, 

 especially when viewed on a white surface, and the next day 

 a faint yellowish tint was visible under a lens. The tail 

 formed a blunt knob projecting beyond the yolk. 



The yellowish hue was more distinct on the 30th March. 

 On the head it was somewhat diffused, as the chromatophores 

 had given off branches. The rows of rounded specks along 

 the sides were only faintly tinted. Both yellow and black 

 pigments were present. The latter (black) were very finely 

 ramose on the dorsum of the snout and on the head, as well 

 as behind the otocysts. Distinct muscular twitchings of the 

 body occurred to-day. 



On the 1st April the embryo more than stretched across 

 the Qgg; but in most the pigment corpuscles remained simple. 

 The heart was minutely papillose internally and trumpet- 



* " On the Eggs, Larval and Post-larval Stages of Teleosteans," Trans. 

 Roy. Soc. Dubl. v. 



t Twelfth Ann. Report Fishery Board for Scotland, pt. iii. p. 219, 

 pi. ii. fig. 8. 



