•WAVE-CTJEEENTS ON SHALLOW-SEA FAUNAS. 269 



AmoDg the Crabs there are at least three methods adopted 

 for resisting wave-currents. 



The rock-crabs (Cancer) fix themselves firmly in crevices, 

 where they can bid defiance to the strongest waves. The 

 swimming-crabs {Fortunus) shovel away the sand with their 

 flat swimming-feet, and speedily gain protection under the 

 surface ; whilst the hermit-crabs {Pagurus), inhabiting empty 

 shells, secure a fair hold on the bottom by the length of their 

 legs, the latter being long in proportion to the size of the bodies 

 of the crabs and their strange coverings. 



Moreover, the swimming-crabs are quite alive to the advan- 

 tages, as well as the disadvantages, of reciprocal currents. I have 

 seen one of these crabs make a rapid passage seawards by swim- 

 ming with the outward-flowing wave-current, and settling down 

 between the sand-ripples on the bottom when the shoreward 

 current commenced to flow. 



Mr. Couch, referring to the habit of the masked crab {Gorystes 

 cassivelaunus) burrowing in the sand, and " leaving the extremi- 

 ties of its antennae alone projecting above the surface," suggested 

 that the antennae might assist in the process of excavation. 

 Having kept one of these crabs in confinement for some little 

 time, I venture to doubt the accuracy of this explanation, seeing 

 that they descend into the sand backwards with the greatest 

 agility, and thus leave the antennae no opportunity of assisting in 

 the operation . I incline to think that the function of the antennae 

 is to maintain a communication between the buried crab and the 

 water above, as without some such connexion there would be a 

 risk of the animals being occasionally buried to a dangerous depth 

 by the accumulation of sand above them *. Mr. W. Thomp- 

 son's statement that the antennae in very small specimens " are 

 much longer in proportion to the carapace than in the adult " 

 (T. Bell, ' British Stalk-eyed Crustacea,' pp. 161, 162) harmonizes 

 well with this hypothesis, as to ensure safety the young would 

 have to burrow to a greater depth compared with the adults 

 than would be proportionate to their size. 



* Note. — When writing the above, I was unaware thatso long ago as 1866 Mr. P. 

 H. Gosse, F.E.S., had criticised Mr. Couch's theory as to the antenna of Corystes, 

 and had expressed his own opinion that their use was " to keep a passage open 

 through the sand from the bottom of the burrow to the superincumbent water " 

 ('Year at the Shore,' pp. 127-131). I much regret the unintentional plagiarism. 

 —A. E. H. 



LINN. JOUEN. — ZOOLOGY, VOL. XVIII. 19 



