CALLINECTES HASTATUS 159 



and then extends backward and forward as the ventral longitu- 

 dinal artery. Remove the nervous system and follow this ar- 

 tery. 



Draw a diagrammatic cross-section through the thorax, putting 

 in one drawing the circulation from the heart through the sternal 

 artery to the limbs and back through the gills to the heart. 



Andrews: The Keeping and Rearing of Crayfish for Class Use. Nat. 

 Stud. Rev., 2, 1906. 



: The Young of the Crayfishes Astacus and Cambarus. Smithsonian 



Cont. to Knowl., 35, 1907. 



: Conjugation in the American Crayfish. Am. Nat. 29, 1895. 



Bumpus: Movements of Certain Lobsters Liberated at Woods Hole. Bui. 

 U. S. Com. Fish, 1899. 



: Embryology of the American Lobster. Jour. Morph., 5, 1891. 



Herrick: Natural History of the American Lobster. Bui. U. S. Bur. Fish, 

 29, 1909. 



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



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

 land Fisheries, 21, 1901. 



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



Pearl and Clawson: Variation and Correlation in the Crayfish. Carnegie 

 Inst. Pub., 64, 1907. 



Pearse : Observations on Copulation Among Crawfishes with Special Refer- 

 ence 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 Stonlach of the Lobster and the Food of Larval Lobsters. 

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



CALLINECTES HASTATUS. (Blue Crab.) 



Crabs may be found in shallow water along shore, where they 

 may be easily observed on quiet days. In what direction 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 them- 

 selves, are they protectively colored, or do they depend entirely 

 upon their weapons for defense ? 



In studying the anatomy of the crab, constant comparisons 

 should be made with the lobster. 



External Anatomy. 1. The body is composed of cephalb- 

 thorax and abdomen. Dorsally note the shape of the carapace 



