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Show 494 PROF. J. E. DUERDEX OX CRABS [Dec. 12, short, its balancing functions might be restored by the increase in its thickness and length. Dr. W. G. Ridewood, F.Z.S., exhibited microscopic sections of the skeletal tube found in the restored tail of one of the Dormice (Graphiurus) exhibited by Mr. Thomas. He showed that the wall was made up of close-set lamellae, producing in a transverse section a fine concentric striation. Lacuna; with numerous branching canaliculi were disposed, regularly in relation with the concentric striations, and the general effect was that presented by a transverse section of the humerus or femur of a Frog. Internally to the bony layers and contiguous with the central jelly was a moderately thick layer, which was clear, homogeneous, and highly refractive. Dr. Ridewood also exhibited, by way of contrast, slides of the skeleton of the restored tail of an Iguana Lizard, the skeletal tube in this case being composed of calcified fibro-cartilage and not of bone. The following papers were read :- 1. On the Habits and Reactions of Crabs bearing Actinians in their Claws. By J. E. D u e r d e n , Ph.D., A.R.C.Sc. (Lond.), Professor of Zoology, Rhodes University College, Grahamstown, Cape Colony *. [Received November 29, 1905.] (Text-figures 72-76.) Prof. K. Mobius, in 1880 (‘ Beitrage zur Meeresfauna der Insel Mauritius und der Seychelles '), described the crab Melia tessellata (Latr.) as having the remarkable habit of holding a living actinian in each clawf. The polyps are carried about in front of the ci-ab, held in a kind of defensive attitude, and it is assumed that the actinians, by means of their stinging-threads, may be of service to the crab as aggressive and protective agents and assist it in securing its food; while, on the other hand, the movements of the crab may serve the actinians by bringing them into the neighbourhood of more prey. The fact of one animal making direct use of an altogether different type of animal whereby to obtain its food, employing it as if it were a weapon or implement, would appear to be unique among the lower animals, and involves questions as to the mutual relationships of the two, the reactions of one towards the other, * Communicated by Prof. H i c k s o n , F.R.S., F.Z.S. t The account is given in a footnote (p. 174) to Dr. F. Richter's Report of the Crustacea of the Mauritius and the Seychelles Islands, the crab with an actinian in each claw being depicted on plate xvi. fig. 19. |