THE INVERTEBRATE COURSE. 123 



do you consider to be the more highly differentiated? Which is 

 better fitted for self-maintainance and self-preservation? Make 

 a table of the functions performed by the body of Amphitrite 

 under two headings ; those without which the animal or species 

 could not survive, and those which are luxuries. Are any of 

 these functions performed in a way which you consider more ef- 

 ficient by animals you have already studied in this course ? 



IV. 

 INJECTION OF BLUE CRAB (CALLINECTES SAPIDUS). 



The location of incision to reach the heart is shown in Fig. i. 

 The injecting syringe should be inserted in horizontal position. 



FIG. i. Dorsal view of the blue crab, showing method of injecting through 

 the heart. Drawn from an injected specimen by Helen Daniels Young. 



