42 Cincinnati Society of Natural History. 
a system of small sinuses owtstde the liver proper. In all 
Vertebrates above Bdellostoma (including Petromyzon), the 
sub-intestinal vein in the adult forms a part of the portal 
system. 
The inferior jugular vein when median and wnpaired, as in 
Petromyzon and some of the higher fishes, always empties 
into the sinus venosus. When faired, as in other fishes, it 
empties into the ductus Cuvieri on each side. Miiller recog- 
nized that the posterior end of the right anterior cardinal 
represented the inferior jugular of other forms, but did not 
describe it as such. According to him (Vergl. Anat. der 
Myxinoiden, p. 209), the inferior jugular always originates in 
the hyoid arch and the under side of the operculums. It 
also commonly receives branches from the muscles of the 
pharynx, vere branchiales inferiores and vene nutritie of the 
gill arches. Its origin in Myxinoids is dorsal to the ventral 
aorta, but its course is ventral toit. Thelarge ‘‘club-muscle,” 
therefore, has a double venous supply. ‘The ‘‘ retractor” por- 
tion is supplied by the inferior jugular vein; the ‘‘ com- 
pressor”’ portion by the lateral anterior cardinals (jugulars). 
The anterior cardinals (or jugulars) of Bdellostoma agree 
in all essential respects with those in other fishes, excepting 
the posterior end of the right cardinal. From the probable 
ancestral form, as represented in Elasmobranchs (viz., sym- 
metrical cardinals, anterior and posterior, flowing into right 
and left ductus Cuvieri on each side) the present arrangement 
in Bdellostoma may easily have arose as follows: 1. An 
anastomosis was formed between the right anterior cardinal 
and the inferior jugular, near the posterior end of the “ club- 
muscle;” 2. An anastomosis of the posterior end of the 
anterior cardinal with the portal system; 3. An obliteration 
of the primitive anterior cardinal vessel just behind each of 
these anastomoses. Furthermore, by a union of the anterior 
ends of the posterior common cardinals, the blood was 
diverted from the ~zgh¢ into the left ductus Cuvieri, and the 
right ductus disappeared entirely. The embryology of the 
cardinal veins, when worked out, will decide whether this is 
the true explanation of the present condition in Bdellostoma. 
In no other fishes does the blood from the walls of the 
anterior body region pass into the portal system. It is said 
30 
