LOBSTEE OE CEATFISH 139 



bread. Injected specimens should be used for studying 

 the circulatory system. They should be injected before 

 being put into alcohol. Drill a hole through the cara- 

 pace over the heart, puncture the latter to let out the 

 blood, insert the canula of the syringe, and, with a firm, 

 steady pressure, inject the starch or gum-arabic injection 

 mass. 



Other materials needed are bone forceps, coarse and 

 fine forceps, large and small scissors, scalpels, hand-lens, 

 compound microscope, bristles, dissecting-needles, acetic 

 acid carmine, dilute hydrochloric acid, normal salt solu- 

 tion, and small piece of raw meat. 



Method of Examination. — Live specimens should be 

 studied in aquaria of sea-water or fresh water as re- 

 quired. Individual specimens may be examined in 

 glass, earthen, or tin dishes of water. Alcoholic speci- 

 mens may be laid on the dissecting-trays or in dishes 

 of fifty per cent, alcohol. In the former case it may 

 be well to mix about one-fourth part of glycerine with 

 the alcohol in which the animal is preserved in order to 

 prevent too rapid drying when exposed to the air ; the 

 glycerine will keep the tissues and organs moist and 

 flexible. 



MOEPHOLOGT 



External Charaoters : 

 A. The entire animal. — ^What is its shape ? Is it bilat- 

 erally symmetrical ? Does it possess well-marked 

 anterior and posterior ends ? "What is its general 

 color ? Compare several specimens to see if you 

 can find any decided variations of shape and 

 color. After having determined the sex of the 

 specimen by studying the appendages (which see), 



