882 PROFESSOR W. C. M‘INTOSH AND MR E. E. PRINCE ON 
ventral fins of ordinary Teleosteans, is absent in the wolf-fish, which has no pelvic fins. 
The carotids pass along the base of the brain to the front of the snout, and the venous 
blood is returned by two large trunks, vn (jugulars), descending at the posterior border 
of each ear (aw), and joining the anterior cardinals to form 
the ductus Cuvieri (see Fig. 3). A very distinct, though small 
vessel (ophthalmic), sends a swift stream of blood backward 
over the eye. 
If we examine the circulation at a stage two months later 
than the foregoing period, its complexity has considerably in- 
creased, not only in regard to the vascularity of the branchial 
Fie. 3._Great vessels near the heart, mellz, but also by the great development of the vessels 
Right side. above and below the vertical aortic trunks. The vessels are 

more numerous than in the salmon one day old, and extend 
beyond the muscle-plates into the marginal fin dorsally and ventrally. 
The action of the heart is interesting, and in an example observed on Ist April it 
was as follows :—The sinus is distended with blood mainly from the large vitelline vein, 
then the auricle fills, and its contraction distends the ventricle. The contraction of the 
latter, again, expands the bulbus, dilating every crevice. Sometimes, as in the salmon, 
the ventricle does not quite empty itself, a feature due probably to the structure of its 
reticulated muscular walls. In the salmon, when the chamber is distended, and just 
before contracting, processes of the red fluid dip into the whitish walls, and show that 
even at this early stage the cavity contains muscular bands and interspaces. In weak or 
dying specimens of the salmon the auricle contracts more sharply than the ventricle, the 
latter having a slower vermicular motion, The current in the large venous trunk 
(cardinal), just before the contraction, often gives a jerk backward, this recoil being 
apparently due to the valves of the auricle, and its effects are visible in the 
remotest part of the venous system, especially in the sac near the base of the tail. The 
shortening of the auricle, a most marked movement in contraction, is towards the 
ventricle—just as the hand would squeeze an elastic bag chiefly at its fundus in order to 
drive the fluid by a jerk out of the muzzle. In these young fishes this organ is the 
ultimum moriens. 
In the salmon of the sixth week the aortic bulb is covered with pigment-corpuscles, 
apparently in the pericardial serous membrane, which elsewhere contains similar pigment. 
A band of muscular fibres is connected with the bulb a little way up, and the fibres are 
probably the same as those observed at the side of the pericardium anteriorly in Anar- 
rhichas. The contractions of the heart are most favourably observed from the left side. 
The heart of Anarrhichas in January had comparatively thin walls, which showed, 
in section, few fibres, but many nucleated cells. The thick region was towards the 
bulbus, into which two conspicuous valvular folds (aortic valves) project. In section, the 
area of the entire organ is cellular, with the exception, perhaps, of the external fibrous 
investment, the cells being apparently bound together by a protoplasmic matrix. This 
