LAND CRUSTACEANS. 93 



box, gave out continually a low, chirping sound, though it was not possible to discover 

 how they did this'. The object of the sound is not clear, and theories on this subject 

 must wait till the question of the hearing of the creatures is decided. They certainly often 

 seem to be affected by sounds, but whether this may not be due to other vibrations 

 started at the same time in the earth and surrounding objects is still doubtful to me, my 

 information on the point being limited to desultory observations made at Minikoi before I was 

 obliged to leave the island. 



While they are not strictly nocturnal animals, the land hermit-crabs are certainly more 

 active by night than by day. They seem to avoid the heat of the sun by preference, and 

 to shelter, during the middle of the day, in nooks and crannies. Their habit of crowding 

 together in any place, where food is to be found, makes them seem gregarious — which, in 

 a strict sense of the word they probably are not. At the same time they may some- 

 times be found collected in considerable numbers for no apparent cause. 



They are not given to fighting to the same extent as the hermit-crabs of the sea. 

 When molested they withdraw quickly into their shells, closing the opening with the big 

 left chela, which is specially adapted for this purpose. In this condition a Coenobita in a 

 strong shell, such as that of Turbo argyrostomus must be an exceedingly tough nut for most 

 animals to crack, and can also fall from a considerable height without injury. If they are 

 unable to withdraw into their shells they will sometimes endeavour to defend themselves 

 with the same powerful limb that is used to close the shell, but it often requires a con- 

 siderable amount of teasing to induce them to do this. The grip of the great chela is 

 exceedingly strong and will easily snap a twig which the animal has been made to seize. 



If an individual be placed on its back, that is with the mouth of the shell upper- 

 most, it will thrust out its body till the shell overbalances and the animal is able to 

 recover the normal position. In moving, they crawl obliquely forward and to the left. From 

 the accounts of eye-witnesses-, it would seem that G. diogenes is considerably swifter than the 

 Indo-Pacific species. 



A series of experiments carried out with the object of investigating the vitality of the 

 animals in fresh and salt water led to the following conclusions: — 



(i) Continuous submersion under water is always fatal after a more or le.ss prolonged 

 period, (ii) There is great individual variation in the length of this period, but the sexes 

 do not differ greatly^, (iii) The creatures are very sensitive to the efiects of overcrowding, 

 (iv) Tinned vessels are more injurious than enamelled ones, (v) There is a difference between 

 the powers of resistance to fresh and salt water in favour of the latter, but the difference is 

 not so great as might have been expected. The greatest length of life in salt water reached 

 by any individual during the experiments was 6 days, but this was exceptional. In fresh water 

 24 hours was not exceeded, (vi) Of the three species, C. perlatus showed the greatest vitality 

 in water and C. clypeatus the least, but the number of individuals of the latter experimented 

 with was small, (vii) Before death the animal generally, but not invariably, comes out of 



' Broderip [Zool. Journ., iv. p. 20-5] quoting from the old " Females with eggs do not differ from others in this 



" Encyclop^die " (Paris, 1751) states that C diogenes makes respect, and the hatching larvae died almost as soon in salt 



a small sound when it is seized. as in fresh water. Had it been possible to rig up a "dipper," 



- Soane, Nat. Hist. Jamaica, ii. p. 272; Catesby, Nat. no doubt some of these might have been reared. 

 Hist. Carolinas, u. p. 33. 



