THE ANATOMY OF CATJDINA COKIACEA. 46S 



the minuteness and ill-defined character of the parts in question. 

 Just before the inner nerve-band dies out, there appears to 

 be only a single space between it and the circumanal ampullar 

 (fig. 10). This may be a continuation of the hyponeural canal 

 or a sudden enlargement of the radial blood-sinus. It is a 

 noteworthy fact that it may contain numerous corpuscles 

 {corf. fig. 10) similar to those in the adjacent ampullse. 



The chief conclusions arrived at in this paper may be summed 

 up as follows : — Caudina coriacea possesses two kinds of papillae 

 at the hinder extremity of the body around the anus. (1) Five 

 blunt radially-placed projections, which contain abundant spicules 

 and are mere solid processes of the body-wall, without nerves or 

 ambulacral vessels. These projections are apparently present 

 only in extreme youth, and may represent anal teeth in a ves- 

 tigial condition. (2) Five radially-situated groups of anal 

 tentacles, containing branches of the radial nerves and of the 

 radial ambulacral yessels, and with loosely scattered spicules in^ 

 their walls. The branches of the ambulacral vessels are swollen 

 out to form circumanal ampullse, the function of which is 

 evidently to assist in protraction and retraction of the anal 

 tentacles. 



The anal tentacles are doubtless homologous with the tube- 

 feet of typical Holothurians, which have undergone a change of 

 function and now serve as tactile organs. Grerould has described 

 how Caudina arenata often lives buried in the sand, with only the 

 tip of the tail projecting. Under these circumstances one can 

 well understand the development of sensory tentacles around the 

 aperture, which is not only an anus but also the entrance 

 to the respiratory organs. Caudina coriacea doubtless has a 

 similar habit, and this peculiar mode of life may also serve to 

 explain how it was that the dredgings of the 'Challenger' in 

 Cook Straits and of Mr. Suter in Lyttelton Harbour only 

 brought up fragments of the " tail," these having apparently 

 been cut off by the dredge while the body remained buried in. 

 the sand or mud, 



Ohristchurch, N.Z., 

 August 27, 1897. 



