240 



ELEMENTARY ZOOLOGY. 



FIG. 85. Hermit crab, in the shell of a Gasteropod. Morse. 



Questions on the Figure. What structural adaptations has the 

 hermit crab to this mode of life? What changes have come as the 

 result of the mode of life? What conceivable gain has such a 

 habit? What animals are cited as symbiotic with the hermit crab? 



FIG. 86. Palamonetes vulgaris. From Verrill. 



Questions on the Figure. Compare the appendages of Palae- 

 monetes with those of the lobster, the crab, and Gammarus. What 

 seem to be the functions of the various appendages, so far as position 

 and form may indicate? 



