238 ELEMENTARY ZOOLOGY. 



lobster fisheries may thus be restored to their earlier 

 fruitfulness. 



The hermit-crab (Fig. 85) is peculiar in that it backs 

 into an empty gasteropod shell, and uses this as a protec- 

 tion to the posterior part of its body. In consequence 

 this part remains soft and becomes degenerate, while the 

 anterior appendages, which extend from the mouth of 

 the shell and are used in the capture of food, have a hard 

 skeleton. 



FIG. 82. FIG. 83. 



FIG. 82. The Zoea of Cancer irroratus. From Verrill. X 7. 

 FIG. 83. Megalops of Cancer irroratus. From Verrill. X 7. 



Questions on Figures 82 and 83. Compare these two stages of 

 the development of. the crab and note the chief changes. Compare 

 also with the adult crab, and write a statement expressing some of 

 the chief changes in its development. Compare both these -larvae 

 with that of the lobster (Fig. 80) . What are the differences between 

 the development of the lobster and the crab. Is the larval crab 

 or the adult crab more like the lobster? What inference would 

 you deduce from this fact ? 



255. The Crabs. The short- tailed crabs are broader and 

 shorter than the lobsters, and have their much reduced 

 abdominal segments turned under the thorax. These 

 are the highest Crustacea, and in their development pass 

 through stages somewhat like the adult of the long-tailed 

 Crustacea (Figs. 82 and 83). They are very varied in 



