880 PROFESSOR W. C. M'INTOSH 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. Shaw'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.t 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-discs 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 occurs from the slow rate of progress along the vessels. 



Circulation in the Trunk. — The circulation in the larvae 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. 



* PI. xxii. fig. 2, Trans. Roy. Soc. Edin., vol. xiv., 1840. 

 t Vide Quart. Jour. Micr. tfci., vol. viii. N.S., pi. iii., 1868. 



