236 Mr. E. R. Lankester on Lithodomous Annelids. 



chitinous setfe would be of much avail against hard limestone. 

 Mr. George Busk, at the meeting of the British Association at 

 Dundee, suggested in discussion that the perforation was pos- 

 sibly eifected, both in this case and in that of Leucodore which 

 I then described, bj means of sand rubbed by the worm against 

 the rock or introduced into its gallery when once begun. 

 This he had witnessed in Pholas. The objection to such a 

 view in the case of either of the Annelids is, that they do not 

 possess the necessary power of lateral movement, or any 

 j[>oint d'appui^ also that they only bore carbonate of lime; 

 and, further, it is impossible to guess how an attack could be 

 commenced on a stone in such a manner. We are reduced to 

 the theory that the gallery of Sabella is formed by the con- 

 stant apposition of the tail of the Annelid to the carbonate 

 of lime. The tail has been proved to be acid, and is therefore 

 a perfectly sufficient cause. 



The boring Leucodore is represented in PI. XI. fig. 7 ; and 

 it will be seen that, whilst the ordinary bristles are situate on 

 each somite, the fifth alone possesses very thick dark-colom-ed 

 setee, more or less blunt at the point (fig. 9). We cannot sup- 

 pose that these have any efifect in perforating limestone, since 

 they are merely chitine, and, moreover, are present in species 

 of Leucodore which do 7wt perforate, and which live by hun- 

 dreds in the silt filling cracks of rocks &c., or construct for 

 themselves rough and fragile tubes. At the same time they 

 may very possibly be efficient in excavating loose material. 

 They are undoubtedly homologous with the dark bristles pre- 

 sent in the anterior region of Chcetopterus^ and perhaps are 

 only rudimentary organs — Natm-e's certificate of a long pedi- 

 gree. The sand-theory fails in the case of Leucodore for the 

 same reason as in that of Sabella. In fact no mechanical ex- 

 planation of the perforation will account for a chemical selec- 

 tion of material. In every case of Ze?;co^ore-perforation to 

 which I have alluded, and with dozens of fragments from va- 

 rious stones, often presenting the most different appearances, 

 and looking more like sandstone than limestone, I have tested 

 for the presence of carbonate of lime, and have invariably 

 found it in large quantity ; all the fragments which I sub- 

 mitted to analysis were rapidly disintegrated imder the action 

 of weak acetic acid. Another fact in favour of chemical action 

 is the extremely clean and sharp character of the galleries, 

 both in Sabella and Leucodore. 



My friend Dr. M'Intosh was the only observer at Dundee 

 who expressed a belief that these Annelids perforate rocks 

 other than carbonate of lime. He said that he had seen 

 aluminous shale so bored ; but I think he had other excava- 



