TRANSACTIONS OF SECTION D. 1093 
tinctive yellow colour, in fact, a rich amber shade. In the latter species the spots 
appear on the seventh day after deposition, and rapidly extend from the dorsum 
almost to the caudal termination. In neither species, however, is the yell-surface 
pigmented. G. merlangus shows no colouration till the eighth day, when nume- 
rous pale yellow spots, having a greenish tinge, appear confined chiefly to the 
dorsum, but soon extending over the whole trunk, the embryonal fin and the 
yelk-surface. ‘The two remaining Gadoids exhibit black pigment only. It appears 
in G. morrhua on the seventh day (in a series which emerged from the ovum on 
the ninth day); but in G. eglefinus (which emerged on the twentieth day) it was 
visible on the eleventh day. The spots are at first amorphous, and numerous on 
the dorsum; but they rapidly extend over the tail, and become densely aggregated 
in the mesenteric region. The ‘shoulder,’ above the pectoral fins is also thickly 
pigmented. The embryo of 7. gurnardus exhibits scantily distributed pigment, at 
tirst of a pale sea-green tint, intermingled, two days later, with yellow corpuscles 
and minute black spots. This colouration also appears in the protoplasmic invest- 
ment of the oil-globule present in this species. 
In the development of the sense-organs, &c., no special features were observed 
in the species studied. The embryo remains quiescent in the lower segment of the 
ovum until the cardiac pulsations commence. The rhythmical movement of the 
heart, many days prior to the existence of a hemal circulation, or indeed of a 
hzmal fluid, is an interesting physiological phenomenon, and is coincident generally 
or slightly subsequent to the appearance of pigment in the epiderm. It is note- 
worthy that the first motion of the embryonic trunk (in each series of ova studied 
in the St. Andrews Marine Laboratory) took place on the day preceding liberation, 
when the tail, now free from attachment to the velk, is flexed and relaxed violently. 
These erratic movements probably assist in facilitating extrusion from the capsule. 
The newly-emerged embryos are extremely sensitive and delicate, and swim in a 
reversed position for some time. Neither mouth nor anus is developed, but 
branchial arches are indicated, though the clefts are incomplete. The Pleuronec- 
tide are even more rudimentary than the newly-hatched Gadoids, and exception 
must be taken to the statement of Mr. G. Brook! that the Gadide differ from all 
other teleosteans in the late formation of the anus. The oral aperture usually 
appears at the end of the first week, and one or two days later the proctodeum 
can be detected. The formation of large sub-epidermal spaces, especially in the 
cephalic region of the embryo, is a remarkable feature, the skin, as Ryder remarks,” 
‘is lifted off, perceptibly, from the underlying structures,’ and the interspace formed 
is filled with a transparent plasma. Young embryos a week old assume a 
very grotesque appearance on account of thisanterior enlargement. Simultaneously 
the epiderm becomes nodulate, the eyes are deeply pigmented, and a simple arterial 
and venous circulation is established. The deutoplasm continues visibly to de- 
crease, though there is no yelk-circulation in the species here considered. 
With regard to the conditions of temperature, so important in these investiga- 
tions, the attempt is made in the St. Andrews Marine Laboratory to keep the 
water in the tanks at the same temperature as the sea outside. The laboratory is 
almost completely surrounded by sea-water, and by a continuous supply from St. 
Andrews Bay, a constant circulation is maintained through the tanks, which is 
highly favourable for rearing young teleosteans. It was thus possible to keep the 
temperature at about 40° F. during March and April, rising to 48° and 50° F, in 
May and June, these being the months during which the species here considered 
were reared and studied. 
4. On the Nest and Development of Gastrosteus spinachia at the 
St. Andrews Marine Laboratory. By Epwarp E. Prince. 
This paper was chiefly a record of observations made upon the nidification and 
development of the ova of this common Teleostean in the St. Andrews Marine 
1 Linnean Society Journal, vol. xviii. p. 304. 
2 United States Fish Commissioners’ Report, 1882, p. 530. 
3 Published in extenso with figures in the Ann. Nat. Hist. for December 1885. 
