Scientific Intelligence — Zoology. 403 



points near the centre. These bodies are highly refractive, and are, 

 for the most part, pretty regularly distributed over the whole convex 

 surface of the foot, but are occasionally congregated into masses. 

 Similar crystalline bodies are imbedded in the edges of the mantle 

 surrounding the foot. In Pholas, the same appearance is presented 

 both in the foot and the surrounding edges of the mantle. Saxi- 

 cava I'ugosa has also the anterior portion of the animal abundantly 

 provided with crystalline bodies like those already described ; so also 

 with the foot and mantle of Patella vulgata. These bodies are con- 

 stantly being shed. Acetic acid has no effect on them ; and in Saxi- 

 cava, strong nitric acid produces no change after several days' im- 

 mersion. Those of Pholas and Teredo appear to be ultimately acted 

 on by this acid, but are never totally destroyed by it. It is by 

 means of these bodies that the author believes the animal rasps 

 down the substances in which they are found. The whole of these 

 animals are also supplied with powerful muscles, by which they may 

 effect the necessary movement for the production of this result. 

 Judffino- from analogy, the author believes that all the boring mol- 

 luscs excavate in the same manner ; none by the rasping or cutting 

 of their valves, none by a solvent, none by ciliary currents. In the 

 same manner he accounts for the gradual disappearance of certain 

 portions of the columella in the Gasteropodous Mollusca ; not by the 

 process of '' absorption,' as has been supposed. 



Mr Philips explained more fully the nature of the boring process 

 carried on by these animals, and thought the author of this paper 

 had thrown much light on the subject. Granules on the tongue of 

 many of the molluscs had been long known. They appeared to be 

 of a siliceous character. Professor Owen stated that there were no 

 a j^riori objections to the theories opposed by the author, and one or 

 another had been adopted by naturalists to explain the phenomenon 

 of boring. At the same time, the inadequacy of these theories for 

 the explanation of some cases had led them to regard the foot and 

 mantle as engaged in the operation ; how, he now, for the first time, 

 was informed. He still, however, thought that an exception ought 

 to be made in the case of the Pholas navalis, which he yet believed 

 must burrow in wood by means of its shell. Professor E. Forbes 

 said, that, having to write on this subject in his " History of the 

 British Mollusca," he had carefully gone over the evidence in favour 

 of all the views adopted, and was not unaware of those of the author. 

 He found little evidence to support the theory of a solvent being em- 

 ployed, or of the agency of ciliary currents ; but he found as little 

 in favour of the siliceous particles of the author. He had carefully 

 examined Saxicava, and could find no siliceous granules. Mr Hen- 

 frey had examined these creatures under the microscope, and had 

 failed to detect any thing of the kind. A chemical examination 

 made by Mr Henry had also failed to detect them. He did not deny 

 that they might be present in Clavagella. Under these circum- 

 stances he had endeavoured to take an eclectic view of the subject. 



