FISH-CULTURAL INVESTIGATIONS AT ST. ANDREWS, SCOTLAND. 251 



a slightly pinkish hue from refraction, while uuder a high power they give the capsule 

 a minutely punctured appearance. If a fragment of the zona be dried on a slide, 

 each of the punctures enlarges and becomes the center of a curiously wrinkled margin 

 with numerous processes, such as might have been due to protoplasmic environment. 

 This appearance was, however, probably due to the wrinkles or folds of the dried zona. 

 The latter in the fresh examples is further marked by faint lines or creases, which in 

 some are crossed by another series of similar lines, so that it resembles the zona of 

 the brill, lemon dab, and sail fluke. The micropyle is very evident and after the plan 

 of that in the haddock; the external aperture, which is in the center of a depression, 

 is smaller than the internal. 



On the fourth day, when the eggs reached the laboratory, the blastopore was 

 closing or closed, the optic vesicles formed, and a broad alar expansion was present on 

 each side. The perivitelline space was small. Development proceeded normally, so 

 that two days later a number of myotomes were formed laterally, besides lenses and 

 otocysts, while slight contractions occurred in the heart. A considerable portion of 

 the tail was free, and a few simple pigment-specks were scattered over it. The embryo 

 jerks body and tail. Next day (May 28) black chromatophores were studded along 

 the sides of the body and the head, and some on the latter and in the proximity of the 

 pectorals were slightly stellate. Each otocyst had two otoliths. The pectorals pro- 

 jected outward as rounded lobes. The tail was much elongated and had a group of 

 black chromatophores at the tip. The perivitelline space was larger. All the ova lie 

 on the bottom of the vessel. 



Before hatching, a greenish yellow hue (by transmitted light) appeared on the 

 head and the tip of the tail. Some emerged on May 30 before noon (ninth day after 

 fertilization). The larva measures about 4 mm. and is characterized by the large 

 pinkish-brown oil-globule, which is generally fixed at the posterior border of the yolk. 

 In some, however, the oil-globule was freely movable, a feature which had not hitherto 

 been observed in such larval forms. By depressing the tail of the larva the oil-globule 

 glides forward to the middle of the yolk, and by elevating the head it mounts to the 

 highest point, viz, the anterior border of the yolk. Nothing could better illustrate the 

 features formerly pointed out in regard to the movement of the oil-globule in the 

 gurnard,* and the passage of the brightly colored globule through its yolk (and not 

 merely at the surface of the yolk as some thought) was in this instance easily followed. 



The free condition of the oil globule of the larval torsk in these instances was 

 probably abnormal, but it is worthy of note. Five conspicuous black touches or bars 

 further distinguish the larva, viz, one on the head and four on the body. The chro- 

 matophores on the head are somewhat irregularly scattered, though a front view of 

 the head in the egg shows that a more or less symmetrical series occur over each eye. 

 The first patch or bar on the trunk is placed rather behind the middle of the yolk, 

 though a little variation exists, and it is rendered the more conspicuous as the black 

 pigment of the subnotochordal region exists beneath. The chromatophores in this 

 and the other areas are very finely ramose. The next patch or bar lies on the muscle- 

 plates behind the yolk; the last is at the tip of the tail, while a less definite one is 

 intermediate. As already mentioned in connection with the embryo, the larv« have 

 a slightly yellowish hue (greenish by transmitted light) on the head, yolk-sac, and the 

 tip of the tail. The rectum is high up on the marginal fin, with the lumen just 



Trans. R. Soc. Edin., vol. 35, p. 687. 



