1896.] MICROSCOPICAL JOURNAL 15 



tliey are partnerships formed, not between individuals of 

 the same species as in the cases previously mentioned, 

 but between organisms of the most diverse kinds associa- 

 ted together for defensive or profit-sharing purposes. 



In the animal kingdom one of the most remarkable, 

 and pei'haps the best known example, is the association 

 of a sea-anemone with a hermit-crab, a defensive alliance 

 of as great an importance as the Triple Alliance itself. 



The hermit-crab (Pagurus striatus) carries generally 

 on its back, or rather on the whelk-shell which it inhab- 

 its, three or four large anemones (Adamsia rondeletii). 

 It would seem at first a great kindness on the part of 

 the crab to carry about these bulky and helpless individ- 

 uals, but the soft-bodied hermit-crab is very glad of an 

 additional protection to the old whelk-shell, and the 

 anemones, though so soft-bodied and apparently de- 

 fenceless, are provided with most formidable organs of 

 defence, in the form of stinging-cells, with which they, 

 like the jelly-fish, keep most foes at bay, and when located 

 on the back of the hermit's shell they serve to keep its 

 enemies too at a distance. In return for this service the 

 anemone receives a distinct benefit in being taken about 

 to new feeding grounds, and, as it is exceedingly vora- 

 cious, it is delighted to be carried in search of its prey. 

 So both parties are pleased; the hermit-crab to so great 

 an extent that, when it moves into a larger shell, it care- 

 fully detaches, by gentle and persuasive pressure of its 

 claws, the sea-anemone from the old shell and plants 

 it on the new abode. 



Here then we have a partnership between two individ- 

 uals of the animal world, a partnership which is of very 

 common occurrence. It will seem perhaps strange to you 

 to imagine such a defensive league formed between a 

 plant and an animal, and yet a number of such asso- 

 ciations are known. 



