880 PROFESSOR W. C. MINTOSH AND MR E. E. PRINCE ON 
in front, and in its course upward it receives several large branches, but in the wolf-fish 
it is generally on the right. S#aw’s figure * shows the vitelline vein in the salmon 
occupying an unusual position; the yolk-sac, moreover, is too small for a salmon one 
day old, and the oil-globule should either be larger, or be represented by several smaller 
ones. The general direction of the small branches is transverse or oblique, the upper- 
most appearing at the posterior margin, and coursing obliquely downward and forward, 
the middle being nearly transverse, and the lowermost transverse and then upward. 
The last main branch collects the blood from the upper part of the sac, and enters the 
great vessel from behind, not from the ventral side. In Anarrhichas, on the other 
hand, the left side has its twigs mainly at right angles to the body, The two large 
trunks of the vitelline veins pass from behind forward and upward to form by their 
junction the great venous trunk, and it is their disposition that gives a character to the 
vitelline circulation, in contrast with that of the salmon. The afferent vessels stream 
downward into these on both sides of the sac, those on the left, however, entering the 
great branch by numerous trunks (Pl. XXI. fig. 2), and thus forming a contrast to the 
right side (Pl. XXII. fig. 3). It is interesting that, after forming a rete on both sides, 
the smaller trunks should again join to form larger vessels which empty themselves into 
the main branch of the side, as shown in the figures above mentioned. The current in 
the smaller wavy trunks becomes slow, thus probably enabling those changes between 
the contained blood and the neighbouring parts to go on efficiently, and on being accom- 
plished the rapid return of the blood to the heart is facilitated by the formation of the 
larger secondary trunks which join the great veins on each side. This arrangement is not 
seen in the salmon, though the vessels do not branch much, and enter the vitelline veins 
by a current not more than two or three blood-dises broad. In both species the supply 
to the sac is posterior, while the returning blood passes anteriorly. 
The absorption of the sac in the wolf-fish took place about the middle of May, so 
that in all probability it occurred at a period similar to that in the salmon. The 
difficulty in preserving special examples, and the great irregularity in the conditions at 
birth, made the exact determination of the period uncertain. The young wolf-fish, like 
the young salmon, exhibits increased swimming power as the sac becomes less, shooting 
upwards into the water at first with a wriggling motion, but later as the sac diminishes 
it swims more steadily. 
In the partial stasis preceding death the vessels of the sac are greatly enlarged, so 
that either the walls of these canals are contractile, or there is a great pressure of blood, 
and the latter certainly oecurs from the slow rate of progress along the vessels. 
Circulation in the Trunk.—The circulation in the larvee which emerged in the 
middle and towards the end of January showed for the most part the ordinary Teleostean 
features. The main points will be detailed in comparison with the salmon, at a somewhat 
later stage, and, meanwhile, the condition on emerging may briefly be indicated. 
* Pl. xxii. fig. 2, Trans. Roy. Soc. Edin., vol. xiv., 1840. 
+ Vide Quart. Jour. Micr. Sci., vol. viii, N.S., pl. iii., 1868. 
