494 PROF. J. E. DUERDE.NT ON GRABS [DeC. 12, 



shoi-t, 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 

 [Graphi'urus) exhibited by Mr. Thomas. He showed that the 

 wall was made up of close-set lamellse, producing in a transverse 

 section a fine concentric striation. Lacunee with numerous 

 branching canaliculi were disposed regvilai'ly in relation with the 

 concentric striations, and the general efiect was that presented by 

 a transvei'se 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 : — 



I. On the Habits and Reactions of Crabs bearino- Actinians 

 in their Claws. By J. E. Duerden, Ph.D., A.R.C.Sc. 

 (Lond.), Professor of Zoology, Rhodes University Col- 

 lege, Grahanistown, Cape Colony^. 



[Received November 29, 1905.] 

 (Text-figures 72--76.) 



Prof. K. Mobius, in 1880 ('Beitriige 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 

 crab, 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 

 ilifterent 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. Hickson, F.R.S., F.Z.S. 



+ The account is given in a footnote (p. 174) to Dr. F. Ricliter'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. 



