378 \^ COELENTERATA ANTHOZOA chap. 



V 



pieces by the crao.- The association, therefore, seems to be one 

 of mutual advantag(|i to the messmates. It is a noteworthy fact 

 that in these associations the species of Sea-anemone associated 

 with a particular hermit crab is nearly always constant. Thus 

 in the English Channel, Adamsia palliata is almost invariably 

 found associated with Uupagurus prideauxii, and Adamsia ron- 

 deletii with Eupagurus bernhardus. But, perhaps, the most 

 remarkable association of this kind is to be seen in the case of 

 the little shore crab of the Indian Ocean, Melia tesselata, which 

 invariably holds in each of its large claws a small Sea-anemone. 

 Mobius, who originally described this case, relates that when the 

 crab is robbed of its Anemone it appears to be greatly agitated, 

 and hunts about on the sand in the endeavour to find it again, 

 and will even collect the pieces, if the Anemone is cut up, and 

 arrange them in its claw.-^ 



Another very interesting association is that of certain fish 

 and Crustacea with the large Sea -anemones of the tropical 

 Australian coast.^ Thus Stoichactis kenti almost invariably 

 contains two or more specimens of the Percoid fish Amphiprion 

 percula. This fish is remarkable for its brilliant colour, three 

 pearly white cross -bands interrupt a ground plan of bright 

 orange-vermilion, and the ends of the cross-bands as well as the 

 fins are bordered with black. In another species a prawn of 

 similar striking colours is found. These companions of the giant 

 Anemones swim about among the tentacles unharmed, and when 

 disturbed seek refuge in the mouth. It has been suggested that 

 these bright and attractive animals serve as a lure or bait for 

 other animals, which are enticed into striking distance of the 

 stinging threads of the Anemone, but how the commensals escape 

 the fate of the animals they attract has yet to be explained. 



In a considerable number of Sea-anemones, such as Actinoloha 

 marginata and A. dianthus, some species of Sagartia, Actinia 

 cari, Anemonia sulcata, and Calliactis parasitica, the fertilisa- 

 tion of the eggs and their subsequent development take place in 

 the sea water.^ In a great many others, such as Bunodcs (several 

 species), Cereactis aurantiaca, Sagartia troglodytes, Bunodactis 



' For recent experiments on this case, see a forthcoming paper by J. E. Duerdcn 

 {P.Z.S.). 



^ Saville Kent, "Great Barrier Reef," London, 1893, p. 145. 

 = O. Carlgren, Biolog. Centralbl. xxi. 1901, p. 480. 



