234 Mr. E. R. Lankester on Lithodomotis Annelids. 



lime (figs. 1 & 2). On breaking off fragments of these stones 

 (often so liard as to defy a heavy geological hammer), the pas- 

 sages were found to extend in many cases to the depth of an 

 inch, and in some cases to two inches and a half, the breadth 

 of the cavity varying proportionately. The excavations in this 

 case were not cylindrical, as with Sahella, but in transverse 

 section presented a keyhole- or figure-of-eight outline (fig. 3). 

 As seen in the drawing, they do not terminate abruptly, but 

 appear to be formed by the beuding-round of a single cylin- 

 drical gallery. Within these galleries, and coiled round so 

 that the head and the tail both point to the aperture, many 

 specimens of the worm which made them were found (figs. 5, 6). 

 The worm does not lie in immediate contact with the stone, 

 -but the interior of the gallery is lined and its substance im- 

 pregnated with a viscid secretion derived from the worm's 

 body. The partition between the two parallel passages of the 

 gallery is often formed solely of this material. Boulders are 

 not unfrequently found which have been entirely deserted by 

 their occupants, or from which these have passed away by 

 death and decay ; and in those cases the animal matter which 

 lines the excavated passages is very easily seen, and sometimes 

 may be peeled ofiT as a black carbonaceous film. 



Having the case of Sabella saxicava in mind, I was fully 

 prepared to ascribe to a chemical action the perforation of the 

 hard limestone boulders by the Leucodore ; for to that genus of 

 Johnston [Poli/dora of Bosc) the worm proved to belong. In this 

 view I received a quite imexpected confirmation on subsequently 

 visiting White Clitf Bay, where the shore is covered with huge 

 masses of chalk rounded by the sea's washing and overgrown 

 with Algaj. A very large proportion of these blocks were 

 perforated on the surface, just as the limestone boulders further 

 west 5 and yet it would be difficult to find two rocks differing 

 more in density and molecular structure than chalk and those 

 limestone boulders. Their only resemblance was in their 

 chemical composition. It was noticed that in this chalk bay 

 the perforations were by no means so closely disposed : there 

 was abundance of material, and therefore no cause for crowd- 

 ing. Specimens of the worms from the chalk-perforations 

 were obtained in great abundance, and proved identical with 

 those from the limestone, whilst the galleries were identical in 

 every respect. Subsequently to this, I received specimens of 

 limestone from Felixstow, on the coast of Suffolk, where the 

 whole shore is clay, masses of soft clay being exposed at low 

 tide, overgrown with weed and abounding with life. Not a 

 single Leucodore-^eYiox2dion is to be found in this clay, though 

 Pholades and Eum'ccp are abundant in it. Here and there in 



