886 PROFESSOR W. C. M'INTOSH AND MR E. E. PRTNCE ON 



have now assumed a nearly vertical position, instead of being directed from above down- 

 ward and forward. This position is due to the changes in the upward bend of the 

 notochord, and the relations of the hypural elements. The regularity of the vascular loops 

 towards the tip of the tail is noteworthy, each corresponding with a prominent cutaneous 

 frill or process of the marginal (caudal) fin. 



Pigment. — On emerging from the egg, about the beginning of February, the larval 

 Anarrhichas shows finely stellate black pigment on the head and other parts, especially 

 along the dorsal region of the pronephros and alimentary canal, and behind the pectoral 

 fins (PL XXI. fig. 1); a considerable number also occur on the adjoining region of the 

 yolk-sac. It so rapidly increases that a conspicuous blackish band soon stretches from 

 the pectoral fins to the anus. The pigment just described as passing along the dorsal 

 line of the alimentary canal is found in section to be deeply seated, and to be scattered 

 near the commencement of the segmental duct — on each side of the aorta and below the 

 notochord. The pigment dips between the involutions of the duct anteriorly, and after- 

 wards forms a lining to the roof of the perivisceral cavity, splitting in the centre to 

 enfold the segmental ducts. It continues all the way back to the urinary vesicle, 

 diminishing much posteriorly, then dips in between the vesicle and the rectum and 

 ceases. In the case of those embryos long retained in the egg, the pigment is abundant. 

 The general hue of the fish is a translucent straw-colour, with the exception of the 

 blackish pigment just referred to. As the latter increases it is found that dorsally, in 

 lateral view, it becomes aggregated largely in two lines above the level of the notochord, 

 and gradually reaches the base of the tail. Much of this pigment is doubtless deep seated, 

 that is, is developed in the membranes of the brain and spinal cord. 



In the beginning of April the blackish dorsal and ventral bands on the side become con- 

 spicuous. Each commences behind the pectoral fin, and envelops the lateral region of the 

 body almost to the lower border of the liver, where it is defined by a straight line which 

 commences somewhat above the notochord in front, and dips slightly in its course until 

 it reaches the anus. It covers the entire alimentary tract, and posteriorly shows 

 numerous dorsal digitations. The head is now so closely covered by the stellate pigment- 

 spots that it assumes a dull slate-colour, and the same hue characterises the anterior 

 region of the body. A double line of pigment runs internally (1) along the tips of the 

 neural spines, processes interdigitating with them, and continuing very distinctly almost 

 to the end of the notochord; (2) the other passes from a point a little behind the head on 

 the surface of the muscle- masses, to cease a little before the other band just described. 

 This outer pigment-layer is within the bases of the spines (interspinous bones). Towards 

 the end of the month a still further increase takes place in the pigment between the snout 

 and the base of the tail, and it extends latterly to the ventral marginal fin. The densest 

 region is at the dorsal margin of the abdomen on each side, and stretching from the 

 pectorals to the anus. The fish laterally shows a silvery lustre (from the peritoneum), 

 with black touches, which form an obliquely striped arrangement (PL XXVII. fig. l). 

 Toward the upper region of the abdomen the colour progressively increases, so that about 



