Kirk. — Heptatrema cirrata Forster. 241 



Art. XXVI. — Some Features of the Circulatory System of Heptatrema 



cirrata Forster. 



By Professor H. B. Kirk, M.A., Victoria College, Wellington. 



[Read before the Wellington Philosophical Society, 4th October, 1911.] 



Plates XVI, XVII. 



During this year 1 obtained several specimens of Heptatrenui cirrata 

 Forster. In this paper I give a short account of the circulatory system, 

 which presents some features of interest. As there are not in New 

 Zealand the publications containing the papers of most of the workers 

 on Myxinoid anatomy, I do not go into any great detail in this paper. 



Ten specimens were at different times injected. Injections were made 

 into the ventral aorta, the dorsal aorta, and usually one of the posterior 

 cardinal sinuses. Although the injection of Heptatrema is often very 

 effective, it is apt to be capricious. Usually an injection thrown into 

 one of the posterior cardinal sinuses suffices to fill the whole venous 

 system, but at times such an injection fails in one part or more. I have 

 not yet attempted to inject the lymphatic system, which, from the extent 

 of the subdermal lymph-spaces, is probably extensive and diffuse. I 

 have found gelatine the most suitable injecting vehicle. 



The circulatory system of Heptatrema presents, as might be expected, 

 many resemblances to that of Bdellostoma, but it presents also some 

 notable differences. The ventral aorta, for example, branches before any 

 afferent branchial arteries are given off; the jugular system achieves 

 great development; the short subintestinal vein passes direct to the right 

 hepatic portal vein, not to the sinus venosus. 



Heart. — The sinus venosus is, as usual, thin-walled, and it presents 

 no considerable dilatation when fully injected. The atrium has thick, 

 spongy, and muscular walls. It dilates greatly when injected, and then 

 often presents a lobulated appearance. The passage from the atrium to 

 the ventricle is guarded by a single pair of deep " pocket " valves. The 

 wall of the ventricle is enormously thick, and its cavity is small. The 

 passage to the short bulbus aortae is guarded by a single " sleeve " valve 

 of peculiar construction. The base of this "sleeve" is attached to the 

 wall of the ventricle, and the " sleeve " projects into the bulbus. It is 

 not, however, free, but each side has a line of attachment to the wall of 

 the bulbus. These lines of attachment are dorso-lateral and ventro- 

 lateral. The terminal portion of the " sleeve " is wider than the basal 

 portion, and the edges of this terminal portion tend to fall together, 

 closing the passage. 



Ventral Aorta. — Except for the short bulbus, there is no median por- 

 tion of the ventral aorta, forking of the aorta taking place immediately. 

 Each division of the aorta runs for about 1 cm. before it fives off 

 the earliest of its afferent branchial arteries. The afferent branchial 

 arteries are long and curved, an arrangement that fully provides for 

 the great dilatation of the pharynx that takes place when large pieces 

 of food are passed along it. Each afferent branchial artery enters the 

 wall of the gill-sac on its posterior aspect just below the point of origin 

 of the excurrent branchial tube. The most anterior of the series of ovi- 

 sacs is supplied by the terminal portion of the division of the aorta. 



