144 TEANSACTIONS 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 (PI. 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 j^rocesses {x). 

 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 diflicuty in making out 

 the intimate relation of these strands to the epithelial 

 lining of the gut, (PL XXXVII, fig. 4 ; PI. 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 joins the aboral 



