Lobster's and Crabs. 101 



ably used as an anchoring apparatus, the latter for 

 seizing articles of food. 



The two succeeding pairs of abdominal limbs are 

 also pincer-like at the extremity; the two following 

 are simply pointed, but still exhibit seven joints. All 

 the abdominal limbs, except the last, carry gills ap- 

 pended to the basal joint, and placed under cover of 

 the dorsal shell. 



The six movable rings which form the ' tail ' of 

 the lobster, bear laterally limbs adapted for swimming, 

 each made up of a basal part, and two flattened 

 appendages external and internal; the last of these 

 segments not only carries the widely expanded 

 swimmer or tail fins, but bears at its hinder extremity 

 also a single median flap or i telson/ sometimes 

 regarded as a separate segment. These movable rings 

 make up the post-abdomen. 



The ear in the lobster is a sac on the upper surface 

 of the first joint of the antennule; the gills lie under 

 the hinder and lateral parts of the dorsal shield. The 

 stomach is a gizzard-like cavity with calcareous masses 

 lining its walls, followed by a narrow soft-walled 

 digestive stomach and intestine, below which lies the 

 nerve-cord, and above it is the heart. 



The crab differs from the lobster not only in shape 

 but in the comparative immobility and small size of 

 its post-abdomen, which is turned in and sunk into 

 a groove. While the young lobster only differs from 

 the adult in the possession of small outer appendages 

 on the walking limbs, and the smaller size of the tail, 

 the crab emerges from the egg in a form utterly 

 unlike the adult, as a little swimming creature with 



