THE CRUSTACEA 121 



in a boiled Lobster. The claws and limbs are long and slender 

 with the exception of the last pair, which are much reduced in 

 size and are either turned back on to the dorsal surface or carried 

 in the branchial chamber. The pretty little Broad-claw Crabs 

 may be found hiding under stones in the rock pools, frequenting 

 much the same situations as their near relations the Galathea 

 Crabs. They have broad, flat claws, with a fringing of short, 

 stout hairs, and are greyish brown on the upper surface. Indeed, 

 so closely does their coloration harmonise with their surround- 

 ings that they readily escape observation. The zoaea stage of 

 these crabs is characterised by the immense length of the spines 

 on the front of the head and at the back, the little creature, as 

 may be seen by the photograph facing p. 116, presenting a very 

 quaint appearance. The Stone Crab (Lithodes maia) has a highly 

 calcified shell, and to the casual glance bears a resemblance to 

 a Spiny Spider Crab, but closer inspection discloses anatomical 

 details which unmistakably show its near relationship to the 

 PaguridecB or Hermit Crabs, and that its ancestors were probably 

 typical shell-haunting crabs which at some period took to a different 

 mode of life, and so gradually lost those characteristics that 

 are associated with the dwellers in a spiral shell as seen in the 

 Common Hermit Crab. 



The Common Hermit Crab is of interest not only on account 

 of its living in a whelk-shell, but also for the curious friendship 

 which exists between it and a sea-anemone that is constantly to 

 be found mounted on the whelk-shell so that it is carried about 

 wherever the Hermit Crab goes. While the anemone benefits 

 in being constantly transported to fresh feeding grounds, and 

 may actually share in the prey captured by the Hermit, the latter 

 probably benefits by being partially screened from view when 

 at rest, when the anemone is fully expanded, and unwelcome 

 visitors may be kept away by the knowledge of the stinging thread 

 cells that clothe the waving tentacles of the anemone. 



The coral islands of the Indian and Pacific Oceans, where coco-nut 

 trees grow, are frequented by a gigantic crab called the Robber 

 Crab (Birgus latro], which often exceeds a foot in length. Darwin 

 gives the following interesting description of it in his account of 

 Keeling Island : " This crab has its front pair of legs terminated 

 by very strong and heavy pincers, and the last pair by others 



