264 Proceedings of the 



Johnston describes it as a soft, almost fluid, reddish-pink pulp 

 or medulla, in organic connection with the polyp. Daly ell states 

 that the tube is replete with a yellowish tenacious mucous 

 matter completely occupying the whole, or accumulated in irre- 

 gular ruddy masses. These naturalists were therefore ignorant 

 of the anatomy of the polypary, though Johnston remarked 

 that the recent stalk was marked by longitudinal pale lines 

 placed at equal distances, which he justly considered were 

 evidences of some peculiar structure in what he termed the 

 interior pulp ; and he inquires, " What is their relation to the 

 currents observed by Mr Lister 1" It is probable that John- 

 ston referred from memory to Lister's discovery of the circu- 

 lation in Tubularia, as the latter writer, in the 124th. volume 

 of the Philosophical Transactions, clearly describes these lines, 

 and their relations to the currents. He remarks, " when mag- 

 nified about one hundred times, a current of particles was 

 seen within the tube that strikingly resembled, in its continued 

 steady flow, the circulation in plants of the genus Chara. 

 The general course of the stream was parallel to the slightly 

 spiral lines on the tube. On the greater part of the side first 

 viewed, it set as from the polypus ; but on reversing the glass 

 trough so as to show the other side, the flow was there 

 towards the polypus : each current thus occupying half the 

 circumference/' " The tube had, between the lines of more 

 conspicuous spots, a granular appearance, and beneath this 

 the currents ran." Daly ell, though he examined a great num- 

 ber of specimens of all sizes and ages, was never able to detect 

 any such circulation, and appears strongly to doubt, although 

 he does not deny, its existence. It certainly is not readily 

 observed in healthy individuals, as the moving fluid is very 

 clear, and generally contains little or none of the granular mat- 

 ter which is carried along by the circulation in most of the 

 hydroid zoophytes. Its existence, however, indicated by the 

 passage of a few flying particles, may be detected in all living 

 specimens, especially in those which have cast off their polyps, 

 and in which the process of the renewal of those organs re- 

 quires the conveyance of solid matter to them from all parts 

 of the stem. Lister's observations were conducted on a single 

 specimen which he had found thrown up on the sea-shore, and 



