Vascular System of Bdellostoma dombeyt. 13 
AN INVESTIGATION OF THE VASCULAR SYSTEM 
OF BDELLOSTOMA DOMBEYI. 
The Cyclostomata derive their interest and importance 
from the fact that they are not only the lowest of the Crazzata, 
but also possess many structural features which are undoubt- 
edly ancestral in their character. As Dr. Ayers has main- 
tained, too little attention has been paid to this class, espec- 
ially to the Myxinoid division. With the exception of 
Johannes Miiller’s ‘“‘Vergleichende Anatomie der Myxi- 
noiden”’ (published 1834-1842), the Myxinoids, especially 
Bdellostoma, have scarcely been touched. A closer examina- 
tion of the anatomy of the blood-vascular system of Bdello- 
stoma, and a discussion of a few points concerning its com- 
parative anatomy in the light of our present knowledge, is 
the purpose of this paper. 
The material used in the following investigation included 
several injected specimens, and a large number of uninjected 
specimens of Bdellostoma dombeyi collected by me during 
the summer of 1897, in the, Bay of Monterey, at Pacific 
Grove, California. Carmine-gelatine was used for injection, 
and the specimens were preserved in alcohol-formalin mix- 
ture (95 per cent alcohol, 6 parts; 2 per cent formalin, 4 
parts). For comparison I have used specimens of Bde/lo- 
stoma forsteri (from the Cape of Good Hope), Petromyzon, 
Myxine, etc., belonging to Dr. Ayers, under whose direction 
the following investigation was made. 
THE HEART. 
Ghioures [TE Ih aise. Ix, Xo XT V): 
The heart is composed of three chambers — sinus venosus, 
auricle, and ventricle. 
The szzus venosus (Figs. I, I, S), (gemeinschaftlichen Kér- 
pervenenstamm of Miiller), is that part of the heart which 
Jour. Crn. Soc. Nat. Hist., Vov. XX, No. 1. I PRINTED OCTOBER 24, I901, 
