238 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 
Durham’s paper, quoted above). In longitudinal sections 
fine fibrils may be seen, especially in the tapering oral 
end. ‘The whole organ is densely crowded with small 
cells, similar as Durham remarks, to the leucocytes of the 
coelomic fluid (Pl. XXXVII, fig. 3). Upon its surface, a 
number of clear vesicle-like spaces may be seen. These, 
in the opinion of the author just quoted, are points at 
which the fluid contained in the tubules is more abundant. 
Upon some of them the cells already mentioned form a 
reticulum by means of their pseudopodial processes (2). 
As far as I can make out there is no regular epithelium 
within or without the membranous wall of the tubules, 
such as is described and figured by Hamann (4). There 
certainly is such an epithelial lining within the tubules of 
the central plexus of Antedon; but in Crinoids the organ 
and its connections appear to me to be of a more highly 
specialised character than in Asterids. Allusion has 
already been made in the introductory part of this paper 
to the so-called gastric blood vessels, which are des- 
cribed as passing from the central plexus to the pyloric 
portion of the gut. I have had no difficuty in making out 
the intimate relation of these strands to the epithelial 
‘lining of the gut, (Pl. XXXVII, fig. 4; Pl. XXXIX, fig. 
1, ghs) and, in the case of one of them, to the central 
plexus. The continuity of the other stand with the latter 
organ is, however, not so obvious, and though I have 
examined it carefully in all my series of sections I have not 
been able to arrive at a definite conclusion with regard to ~ 
it. Whatever the true nature of these strands may be, 
they are certainly something more than “ mesenteric 
bridles,’ under which term MacBride (5) alludes to their 
presence in Ophiurids. 
At or near the point from which the gastric strand 
passes from the central plexus, the latter joms the aboral 
