1905.] 



BEARING ACTINIANS IN THEIR CLAWS. 



495 



the manner in which the combination is bi-ought about, and the 

 peculiarities which each may exhibit in correlation with the 

 commensal habit. 



The note by Mobius is as follows : — " I have collected about 

 50 male and female examples of Melia iesseUaia, all holding in 

 each claw an Actinia prehensa [text-fig. 72]. The hooks on the 

 inner border of claws are bent in a peculiar manner, so as to 

 hold fast the actinian. I have never been able to withdraw the 

 actinian from the crab without injury. If the pieces of the ac- 

 tinian which had been thus withdrawn were allowed to remain in 

 the vessel along with the Melia tessellata, the latter again seized 

 them in a short time. If the actinians were cut into pieces they 

 were again found iii a few hours in the claws of the crabs. 



Melia tessellata from Mauritius, holding an actinian in each claw (Richter) 



" It is very evident that the actinians by means of the threads 

 of their stinging-cells are able to assist the crab in securing its 

 prey, for which the actinian has the advantage of being carried 

 from one place to another, and by this means is brought into 

 touch with more animals which serve them as food. We have 

 here a very interesting case of commensalism." 



Nothing further seems to have been contributed to this 

 peculiar relationship between crab and actinian until Mr. J. 

 Stanley Gardiner's expedition to the Maldive Islands. In the 

 account of the marine crustaceans of this expedition, Mr. L. A. 

 Borradaile (' The Fauna and Geography of the Maldive and Lacca- 

 dive Archipelagoes,' vol. i. pt. 3, p. 250) writes of Melia tessellata 

 (text-fig. 73, p. 496) as follows : — " The crab, which lives, like 

 Trapezia, among the living branches of coral stocks, holding on by 

 its long slender legs, has for some time been known to be in the 

 habit of carrying in each chela a small sea-anemone. The object 

 of this habit is not known, but it is certainly a voluntary act on 



