483 
between the sinus of the piston and the inferior jugular vein; 
c) the connection between the deep anterior cardinal vein and the 
infra-capsular sinus has been already described; d) anteriorly there is 
a conspicuous connection between the sub-cutaneous sinus and the 
internal sinuses. This aperture is dorso-lateral, and is bounded by 
the posterior extremity of the tentacularis posterior and the second 
myotome—forming a nick in the latter muscle (cf. Part II Plate IV 
Figs. 8 and 9 of my Myxine monograph). The channel connected 
with the above aperture is at first of large diameter, and passes in- 
wards and backwards dorsal and lateral to the fused trabecular and 
pterygo-quadrate cartilages. It then travels obliquely through the 
second fenestra of the skull, and communicates with a large lateral 
sinus just underneath the myotomes occupying the position of the 
third fenestra of the skull. There is a valve here which apparently 
permits a central and not a peripheral flow of the contents of the 
sinus. Behind the second fenestra, it occupies the mesial angle formed 
by the fusion of the “hyoid arch” and the auditory capsule. Im- 
mediately behind this fusion it divides into two vessels—a dorsal 
and a ventral. The latter is at first wrapped round the superior 
lateral cartilage, but soon expands ventrally into the very extensive 
latero-ventral sinus situated immediately under the parietal + obliquus 
muscles, of which it forms the anterior narrowed extremity. The 
former accompanies the lateral edge of the diminishing auditory capsule 
and the parachordal cartilage dorsal to the velo-spinalis muscle, and 
finally takes up a lateral position in the skeletogenous layer of the 
sheath of the notochord. It then becomes the irregular lateral 
notochordal sinus situated latero-ventrally in the triangular space left 
by the meeting of the myotomes and notochord, which itself com- 
municates with the large sinus lying immediately over the gut. 
The relations between the subcutaneous sinus and the internal 
vessels may be demonstrated by a simple injection experiment. If 
the needle of the syringe be pushed through the skin, and the sinus 
filled with the injection mass, it will invariably be found that the 
vascular system generally is more or less injected. In four such 
injections the following results were obtained: 1. The caudal heart and 
caudal vein, the posterior cardinal veins with their segmental veins and the 
vessels of the segmental ducts, the portal vein, the peribranchial sinuses 
and the associated ventral longitudinal sinus, the inferior jugular vein, 
the ventricular sinus, both anterior cardinals and the cranial sinuses 
31* 
