REPORT ON PHORONIS BUSKII. 15 



This would seem to be a furtlier develoj^ment of smaller patches of tlic same kind 

 in the anterior spaces, which form just behind the nerve-centre. These have various 

 epithelial patches or cushions on their inner surfaces, and finally unite and Ijecome 

 continuous with the intestinal area in which the apparatus above noted occurs. In 

 longitudinal sections these spaces often show a peculiarly wrinkled appearance anteriorly 

 — from the arrangement of the epithelial bands. Such may represent a kind of sensory 

 apparatus. 



No distinct lining-membrane was visible in the spaces of the body-cavity posteriorly, 

 but an endothelium (peritoneum, Caldwell) may be found in fresh examples. All that 

 could be said was that the numerous fibres entangled many free cells and granules in 

 certain regions. The blood-spaces of the anterior region, again, show in many parts a 

 finely arranged epithelium (tessellated), the cells of which, moreover, stand prominently 

 outward like minute villi in lateral views. 



The posterior body-cavity is also traversed by the radial muscular fibres, which 

 anteriorly pass towards the centre in definite bands (PI. I. fig. 4). In young specimens 

 the anterior region of this division is almost wholly occupied by the large gullet, the 

 intestine and the radiate and longitudinal muscular fibres, the body-cavity being limited 

 to the chinks between these. 



Metschnikoff mentions that he found many colourless cells in the body-cavity of 

 the young Phoronis, the elongated forms especially interesting him from their resem- 

 blance to sperms. Dyster, again, states that no perivisceral corpuscles occurred in his 

 specimens. 



Digestive System. 



The mouth opens at the bottom of the anterior or ventral (and outer) whorl of the 

 branchial apparatus, the basal web of which is continuous from side to side (PI. III. 

 figs. 1 and 3). The arrangement of the parts forms a spacious funnel, terminating in 

 the mouth. The bases of the outer series of tentacles are continued for some distance 

 into this oral funnel as elevated and ciliated ridges, and thus at a given level this 

 surface differs from the opposite one, where the flap-like extension of the mucous layer 

 occurs. The latter covers the base of the second branchial whorl, and consists of a 

 greatly increased hj^odermic layer continuous with that coating the oral chamber. It 

 terminates in a somewhat free margin anteriorly {i.e. distally), and the tissue forming the 

 tip has a foliate arrangement in section (PI. III. fig. 1, a). A layer of basement- tissue is 

 continued from the reticulated coat of the gullet (sub-mucous), but this ends at the 

 commencement of the free margin. The mucous lining of the mouth thus passes up 

 the funnel all round to meet the hypodermic investment covering the bases of the 

 tentacles. 



The first or pharyngeal part of the alimentary canal has its walls transversely 



