882 PROFESSOR W. 0. 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 (cm), and joining the anterior cardinals to form 

 the ductus Cuvieri (see Fig. 3). Avery 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 

 lamellae, but also by the great development of the vessels 



Fig. 3. — Great vessels near the heart. . 



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 1st 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 



