CALLINECTES 177 



male the openings of the sperm ducts on the coxopods of the 

 fifth pair. 



Internal Anatomy. — Remove the entire dorsal part of the 

 carapace. 



X. Posterolateral^ are two firm prominences, the flanks, 

 containing muscles. What are these muscles for? Anterior 

 to these are the gill chambers covered by a thin cuticle. Re- 

 move this and note the gills with their tips converging 

 medially. 



2. Between the gill chambers and flanks is the delicate 

 pericardium. Remove this and find the heart with its ostia. 

 Anteriorly it sends out an ophthalmic artery and two an- 

 tennary arteries. Just anterior to the heart are muscles 

 which were attached to the shell. What organs do they sup- 

 ply? The antennary arteries pass through the heads of a 

 pair of the muscles. 



3. In front of the gill chambers are the gonads. In the 

 female the orange ovary will be seen lying on the yellow 

 liver. In the male the slender, wavy, white cord, the testis, 

 lies in approximately the same position. 



4. The heart is attached to the pericardium by muscular 

 strands. Cut these, and the three anterior arteries, and re- 

 move the heart, noting the two hepatic arteries beneath the 

 antennary arteries, the great sternal artery passing down- 

 ward from the under side, and the small abdominal artery 

 just behind the last. 



Draw dorsal and ventral views of the heart to show the 

 ostia and the origins of arteries. 



5. Cut across a gill and notice its afferent and efferent 

 vessels. The latter is continuous with one of the sinuses 

 which empty into the pericardial cavity. Can you determine 

 how many sinuses there are? Do you understand how the 

 heart receives blood? 



Reproductive System. — Beginning anterolateral^, on one 

 side, dissect out the reproductive organs, noting at the same 

 time the distribution of arteries. 

 12 



