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



the surface of the yolk, and though a large posterior vessel shows a more rapid flow than 

 the rest, still it is not so swift as in the anterior trunk. The great anterior vessels 

 have a shorter and more nearly horizontal course, and do not wander over the yolk as 

 observed in February. 



The blood-discs of the wolf-fish present no special feature of note, though they some- 

 times undergo peculiar changes of form after escape (PL XXL fig. 5a). 



In about a fortnight after hatching, the yolk-sac has materially diminished, forming a 

 rounded projection anteriorly, somewhat less in bulk than the head above it. In the ex- 

 ample studied, the globule was found to have passed to the right side (PL XXI. fig. 3), 

 and a considerable portion of the yolk-mass lay in front of it. The vitelline vein was thus 

 carried backward by the peculiar displacement of the oil-globule. The smaller vessels 

 curved round the anterior border of the globule to join the vein or its branches at various 

 angles, but in the main more or less transversely. A similar arrangement occurs pos- 

 teriorly, though the branches may, in lateral view, often have a shorter course, since the 

 great vein is, inferiorly, nearer the posterior than the anterior border. On the left side 

 (PL XXI. fig. 3a) the anterior vessel is now superior in position, and is somewhat trans- 

 verse in direction, while the other branches are much shortened, and their course is 

 chiefly downward and forward. In those most advanced (PL XXVII. fig. 1) the yolk- 

 mass is noticeable only as a projection in front, for the posterior end merges, as it were, 

 in the abdomen. The oil-globule now lies under the branchiostegal rays. It is note- 

 worthy that the absorption of the yolk was accomplished in some cases at the beginning 

 of May. Moreover, while the young fishes were comparatively delicate in their earlier 

 stages, an alteration seemed to ensue about the time of the absorption of the yolk, so 

 that they became more hardy — their tenacity of life being so great that examples 

 appeared to surfer little though left unchanged for some days in a very small quantity 

 of sea- water. 



We have explained that the outline of the yolk-sac in Anarrhichas is quite different 

 from that in the salmon, being spheroidal instead of elongated and sloped posteriorly. 

 It corresponds, in fact, rather to the condition in the embryonic salmon before hatching 

 — say the 40th day in those which hatch on the 60th day. The shape in the salmon 

 also shows the changes of outline during absorption more boldly, the sac in the healthy 

 fish (PL XXII. fig. 4) becoming gradually attenuated posteriorly (Ibid., figs. 7 and 8), and 

 occasionally in the more vigorous specimens, as Sir J. Gibson Maitland has shown, a 

 portion of this region is constricted off and shed. Such a condition is not possible in the 

 spheroidal yolk of Anarrhichas. Further, the great abundance of oleaginous globules in 

 the upper part of the yolk in the salmon, and the occurrence of smaller globules through- 

 out the entire mass, is wholly unlike Anarrhichas. In the latter species the single large 

 oil-globule is nearly constant in position, but in the salmon this is certainly less so, though 

 the oleaginous spheres are towards the upper region, and often on the right of the embryo, 

 yet during absorption of the yolk they become more or less posterior in position. At no 

 period does the globule in Anarrhichas pass backward other than the slight degree shown 



