206 ALONG THE FLORIDA REEF. 



As the doctor had encouraged the boys to 

 discover protective resemblances, this was an in- 

 teresting addition to a number of mimics they 

 had found. 



Later Tom found a cactus or prickly-pear 

 branch bearing the ripe fruit, and clinging to it 

 one of the big purple land-crabs {Gecarcinus) 

 common on the keys. He was trying to obtain 

 the fruit, and did not notice the crab clinging to 

 the leaves until he almost touched it, which the 

 doctor pronounced a most interesting instance of 

 protective resemblance. "You can see, boys," 

 said the doctor, '' the application of this : the 

 crab was certainly protected by its resemblance 

 to the fruit for the time being." 



Dick had the cast of a shell of a white spirit- 

 crab on a patch of white sand to illustrate its 

 habit and another example, and the doctor 

 pointed out the fact that these crabs were never 

 seen away from the white sand or in the busk 

 where it was covered by the yellowish leaves of 

 the bay-cedar, while the purple crab was never 

 seen away from the interior or upon the domain 

 of the spirit-crabs. It was Harry's good fortune 



