494 PROF. J. E. DUERDEN ON CRABS [ Dee. 12, 
short, its balancing functions might be restored by the increase 
in its thickness and length. 
Dr. W. G. Ridewood, F.Z.8., 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 lamelle, producing in a transverse 
section a fine concentric striation. Lacune 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. Duerpen, Ph.D., A.R.C.Se. 
(Lond.), Professor of Zoology, Rhodes University Col- 
lege, Grahamstown, Cape Colony *. 
[Received November 29, 1908. | 
(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 claw. 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 
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 invoives questions as to the mutual 
relationships of the two, the reactions of one towards the other, 
* Communicated by Prof. HicKson, F.R.S., F.ZS. 
+ 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. 
