38 TROPIC DAYS 



between the slow and feeble Synapta, one of the most 

 primitive of sea things, and the brilliant, agile fish may 

 be another instance of commensalism. 



No one who parades a coral reef can fail to be im- 

 pressed by the various means adopted by its weaker 

 denizens to evade the consequences of conspicuousness. 

 Among the vast multitude of creatures, mostly hostile 

 to each other, few are more remarkable than the crabs, 

 not only on account of form and habit, but for care of 

 themselves during the periodic casting of their shells. 

 They therefore represent an entertaining study and a 

 never-ending source of pleasure to the observer, who, 

 as he happens on some fantastic member of the family, 

 wonders, remembering his Shakespeare, what impossible 

 matter will Nature make easy next. Dreamy little 

 ripples were laying on the strands sprays of seaweed, 

 torn from the reef which was not quite out of the influence 

 of the easterly swell. The conditions were ordinary, 

 but one fragment made itself noticeable by slight, 

 almost undiscernible, but still distinctive efforts to 

 regain the water, whence it was separated by a few 

 inches. Seaweed alone was visible as it rested on the 

 palm of the hand. Presently it moved hesitatingly and 

 with infinite slowness, and, being reversed, revealed 

 itself as a "watery" crab under living disguise. The 

 specimen was sent to the Australian Museum, Sydney, 

 where it came under the hands of my friend Mr. Allan 

 R. McCulloch, who devotes himself to the phenomena 

 of the sea; and since his references to it are explicit 

 and authoritative, they will be more acceptable than 

 generalities from an uninformed pen: "The crab you 

 sent is the second specimen known of Zewa banfieldi, 

 which I described from a dried specimen received from 

 you some years ago. Not only the species, but the 

 genus also, was unknown until you gave me the oppor- 

 tunity of describing this interesting beast. It is one of 



