64. A. ©. OUDEMANS. 
In the slices between the regions of the upper and lower 
brain commissures I observed in the gelatinous tissue between 
the proboscidian sheath and the brain-masses a larger vessel 
than the other. They approach each other til] they come 
beneath the proboscidian sheath, and communicate with the 
dorsal vessel, which only in this single slice lay in the 
sheath, the four following in its circular muscular layer, and 
in the fifth already beneath the sheath. 
Behind the lower brain commissure I saw the vessels again 
separated, running downwards till they lie beneath the level of 
the nerve-trunks. 
Behind the brain we again have an cesophageal and an intes- 
tinal region. 
In the cesophageal region I again observed the same small 
vessels in the two layers of gelatinous tissue, uniting with one 
another by branches traversing the inner longitudinal layer. 
The vessels within this layer also communicate with the three 
longitudinal vessels. They are all arranged in certain regions. 
Beneath the cesophagus transverse vessels run from the one 
lateral vessel to the other. From the median vessel to these 
transverse vessels, rarely directly to the lateral, other transverse 
vessels occur. But also transverse vessels, hitherto never 
seen, running over and above the proboscidian sheath, con- 
necting the two lateral and passing towards the nerve-chords, 
are everywhere to be observed. It is very probable that 
between all these transverse vessels, which all resemble one 
another (as fig. 71), there still exist connecting vessels, so that 
the whole is a vascular network. This, however, is not easily 
to be demonstrated in transverse sections. 
In the cesophageal region two longitudinal vessels are very 
often visible above the nerve-trunks, therefore dorsolateral. 
These did not always occur, so that 1 do not believe that there 
is (on each side) one uninterrupted longitudinal vessel, but 
fragments of it. The transverse vessels which go over the 
proboscidian sheath, always opened into the longitudinal vessels 
above the nerve-stems, where they occurred. These longitu- 
dinal vessels thus are connecting vessels between the transverse 
