HOMARUS, CALLINECTES 175 



Huxley: The Crayfish. An Introduction to the Study of Zoology. 1884. 



Mead: Habits and Growth of Young Lobsters. Rhode Island Com. 

 Inland Fisheries, 21, 1901. 



Paul: Reflexes of Autotomy. Proc. Roy. Soc. Edinburgh, 35, 1915. 



Pearl and Clawson: Variation and Correlation in the Crayfish. Car- 

 negie Inst. Pub., 64, 1907. 



Pearse: Observations on Copulation Among Crawfishes with Special 

 Reference to Sex Recognition. Am. Nat., 43, 1909. 



Steele: Regeneration of Crayfish Appendages. Univ. Missouri Studies, 

 2, 1904. 



: Regeneration in Compound Eyes of Crustacea. Jour. Exp. Zool., 



5, 1907. 



Williams: The Stomach of the Lobster and the Food of Larval Lob- 

 sters. An. Rep. Com. Inland Fish., Rhode Island, 37, 1907. 



Wood and W T ood: Mechanism of Autotomy in Decapod Crustaceans. 

 Jour. Exp. Zool., 62, 1932. 



CALLINECTES SAPIDUS (Blue Crab) 



Crabs may be found in shallow water along shore, where 

 they may be easily observed on quiet days. In what direc- 

 tion does the animal normally move? How are the legs 

 used? What is the attitude of defense? Determine how the 

 blue crab swims. What do crabs apparently use for food? 

 Do they conceal themselves, are they protectively colored, 

 or do they depend entirely upon their weapons for defense? 



In studying the anatomy of the crab, constant compari- 

 sons should be made with the lobster. 



External Anatomy. — 1. The body is composed of cephalo- 

 thorax and abdomen. Dorsally note the shape of the cara- 

 pace and the position of the abdomen. The size of the 

 abdomen differs in male and female. To what use is the 

 larger abdomen of the female adapted? 



2. Note the first antennae, second antennae, and eyes, and 

 see how they are packed away in recesses in the carapace. 

 In the living animal see if any of these are frequently moved. 



3. The third maxillipeds are flattened and cover the other 

 mouth appendages. 



4. Straighten the abdomen and note the anus. Compare 

 the abdomen of a male with that of a female and both with 

 that of the lobster. The dorsal side of each segment is 



