CRABS, HERMIT-CRABS, AND OTHER CRUSTACEANS. 139 



waters, as well as a little creature known as the sowbug, which 

 is common under stones and boards in damp places. By far 

 the larger proportion of these animals are found in salt-water. 



Pupils having access to the sea-coast will find along the 

 shore, and in pools of water left at low tide, a number of 

 species unlike any thing found in fresh water. 



The common crab may be studied and compared with 

 the lobster. It will be found that the crab has the large 

 claws, little legs, mouth-parts, antennae, and other details 

 similar to the lobster and crawfish. The body, however, 

 is entirely unlike in shape ; instead of being long and cylin- 

 drical, it is wide and flattened, and the long, jointed abdomen 

 so characteristic of the lobster and crawfish is quite concealed 

 in the crab. At first sight, the creature would appear to 

 have no portion corresponding to this part in the lobster, 

 but beneath the body there will be found a close-fitting piece 

 composed of segments or joints, and, if this be raised or 

 opened, the relation between this small piece and the large 

 jointed abdomen of the lobster becomes at once apparent. 



The crab carries her eggs attached in masses to the ab- 

 dominal appendages which are arranged in pairs on the 

 segments of the abdomen, as in the lobster. 



In the following figure, which represents a crab carrying 

 her eggs, a comparison of parts may be made between it and 

 the crawfish or lobster. 



The eggs as they are laid are covered with a sticky fluid, 

 which thickens into threads and holds the eggs together and 

 also holds them in masses to the abdominal appendages. 



