AMPHIOXUS LANOEOLATUS. 
381 
in this region. The right dorsal aorta is said by Langerhans 
to communicate with the right aortic arch, but I doubt this. 
I am not very certain on the point, but I think that it ends 
blindly. Its place is taken in the praeoral region by a branch 
given off from the “ aortic arch,” which runs forward in the 
substance of the notochordal sheath on the right side, parallel 
with the forward continuation of the left aorta, and these two 
vessels undoubtedly communicate beneath the notochord by a 
transverse channel. Finally, the right-side vessel, like that of 
the left, appears to communicate with the coelomic cavities of 
the anterior myotomes. 
Schneider has described a series of lateral vessels given off 
from the dorsal aortae and running into the primary and 
secondary (or tongue-like) bars of the pharynx, through 
which they are supposed to communicate with the cardiac 
endostylar vessel. I have not been able to trace these lateral 
branchial vessels in transverse sections, though I have traced 
a branch from the endostylar vessels into each primary bar 
(see PI. XXXVI B, figs. 4 to 9). 
Upon the inner face of the epipleura below the atrial tunic 
a blood-vessel has been described by W. Muller (13), running 
longitudinally. The vessel is seen especially in specimens 
where the gonad pouches are rudimentary and is related to 
their development. It furnishes capillaries to the testes, but 
the connection between it and other blood-vessels has not 
been observed. 
Upon the wall of the intestine and upon the wall of the 
caecum there are blood-vessels. Those on the intestine are 
large and more numerous in its posterior region. They gather 
together anteriorly and are continued into the endostylar or 
cardiac subpharyngeal trunk, where the alimentary tract en- 
larges to form the pharynx. The vessels on the caecum form 
a network which has been described by Langerhans. They 
give rise to a network of capillaries, and together with the 
capillaries described by the same author in the testes, are 
the only capillaries present (so far as my own conclusions go) 
in Araphioxus. The vessels of the caecum communicate, 
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