TUBE OF PANTHALIS. 183 



be produced. An examination of the hardened and 

 embedded sections of tubes first made ; and of fresh 

 sections of tubes in their natural condition ; and an exter- 

 nal examination of the tubes themselves under running 

 water (bearing in mind the bursting action possessed 

 and exercised by the forepart of the animal's body) afford, 

 I think, a simple explanation. 



The sections shew that the layers, although apparently 

 parallel, do not run horizontally the full length of the 

 tube, but all curve outwards, and it is due to this fact, 

 that Panthalis is able to construct a tube of so great 

 thickness. The process, most probably, is as follows : — 

 A moderately thin tube is first formed, consisting of cob- 

 webs and mud. In consequence of the layers being added 

 internally, the tube would soon become inconveniently 

 small, and the animal thereupon burst the anterior portion 

 (as I saw it burst its original burrow) by expansion of the 

 forepart of its body, thus throwing the mouth of the tube 

 backwards. It then proceeds alternately with the addition 

 of more internal layers and the bursting process, by which 

 means the free ends of the internal tubes are successively 

 thrown outward and the layers are made to take the 

 outward curve above referred to, the final effect being that 

 of a series of hollow truncated cones, one inside another. 



That this is the case is proved both by the fresh section 

 in which the layers can be separated, and by an external 

 examination of the tube masses under running water. By 

 the latter means the different tubes can be partially folded 

 back, but as the split side is always made good in the 

 formation of the new inner tube to which it is attached, 

 these tubes can only be folded back for a portion of the 

 circumference. The long straggling mucus threads which 

 always accompany the tubes are probably formed by the 

 animal when exploring its surroundings. 



