822 PROFESSOR W. C. M'INTOSH AND MR E. E. PRINCE ON 



transverse bands which disappear when they attain maturity. In one fish, viz., the ling, 

 the post-larval stage is uniformly tinted, the next stage longitudinally striped, the third 

 transversely barred, while in the adult it is uniformly tinted as in the older post-larval 

 condition. No rigid rule can thus be held. 



Gadus aeglefinus, L. — The ova of the haddock are about *058 in., varying a little, e.g. 

 from 1*65 mm. to 1'5 mm. The development of the embryo ranges from six days in 

 June to twenty in March.* Thus a series received from Granton presented on the 

 second day (22nd March 1885) a blastodermic cap - 4 mm. in diameter. It reached the 

 equator on the fourth day. While the keel of the embryo indents the yolk, the head is 

 defined, and everywhere shows further progress. On the fifth day the optic enlarge- 

 ments are distinctly outlined. Faint indications of pro to vertebrae (four to five in number) 

 appear in the anterior caudal region, and scattered black pigment-specks show on the 

 sides and dorsum. On the seventh day, at 9 a.m., the blastopore had closed, but 

 Kupffer's vesicle was not apparent till next day. The lenses of the eye are fully 

 formed, and the heart is represented by a granular patch. On the tenth day the various 

 regions of the brain were defined, with the nasal pits, the otocysts, and an opercular 

 cleft ; the liver is indicated on the ventral aspect of the alimentary canal. No cavity is 

 visible in the heart ; the latter pulsates on the eleventh day about ten times per 

 minute, though occasionally a little more rapidly, and shows a somewhat triangular 

 cavity. 



The pigment-spots are more numerous and more elaborately stellate on the twelfth 

 day, especially on the dorso-lateral regions above the pectorals. A lateral fold arises 

 behind the latter and passes along each side. The lumen of the mesenteron has notably 

 enlarged next day on the dorsal side of the liver, but it diminishes very much as it 

 approaches the cephalic region. On the fifteenth day the cephalic region has increased 

 in size, and the body has considerably lengthened. Embryonic rays have appeared 

 in the marginal fin. The heart pulsates on the seventeenth day about thirty times 

 per minute. The eyes have a punctate appearance from the development of pigment, 

 and the first branchial cleft is distinct. On the eighteenth day the eyes have black 

 pigment. A second branchial cleft occurs on the ventral side of each otocyst. The 

 liver has largely increased and projects into the yolk-sac. The pectorals show a distinct 

 rim. The alimentary canal is filamentary anteriorly, and ends blindly in an enlarge- 

 ment posteriorly. Three branchial clefts are visible on the nineteenth day, and the 

 pulsations of the heart are forty per minute. A buccal chamber is continuous with the 

 mesenteron, which has a flexure to the right of the embryo. The segmental ducts and 

 the urinary vesicle are well advanced. 



The embryos emerged on the twentieth day 3 mm. in length, and with a yolk-sac 

 "5 mm. in its long diameter. They attempt to progress with the yolk-sac downward, 

 but at rest are inverted. The black pigment-corpuscles are grouped somewhat densely 

 behind the otocysts, and extend backward a little beyond the commencement of the 



* In contrast with the ova fertilised on the 24th April, and hatched on the 3rd May — that is, in nine days. 



