CALLINECTES HASTATUS. 145 



5. The ventral side of the cephalo-thorax is covered by the 

 sternal plastron. Note the eight sterna and six pairs of lateral 

 episterna, the anterior pair of which is very small. 



6. In the female find the openings of the oviducts in the 

 sixth sternum. 



Make a drawing of the ventral side. 



7. Expose the gill chamber and compare the gill distribution 

 with that of the lobster. 



8. Remove the left third maxilliped entire, and compare it 

 with the same appendage of a lobster. The protopod is com- 

 posed of two segments (coxopod and basipod). The endopod 

 has five pieces (ischipod, meropod, carpopod, propod, and dactyl- 

 opod). The exopod has two large and many small segments. 

 Attached to the coxopod laterally is an epipod which extended 

 into the gill chamber. 



9. Remove the remaining mouth appendages on the left side 

 and compare them with the third maxilliped. They are: second 

 maxilliped bearing epipod and two small gills; first maxilliped 

 with an epipod; second maxilla with a flattened exopod, called 

 the scaphoghathite, which is made up of both exopod and epipod 

 and which has a special function that should be understood; 

 first maxilla, thin and leaf -like; mandible with two hard rods 

 for the attachment of muscles. 



10. Detach and examine one each of the eyes, antennules, and 

 antennce. On the flattest side of the basal joint of the anten- 

 nule note a dark suture the scar of the former opening into the 

 otocyst. Do you understand what function is performed by the 

 otocysts? Near the base of the antenna find the opening of the 

 renal organ (green gland). 



11. Compare each of the five walking legs (pereiopods) with 

 the third maxilliped. Which part, endopod or exopod, is lack- 

 ing? Which bear forceps or chela3? Why is this so? Note in 

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

 fifth pair. 



Internal Anatomy. Remove the entire dorsal part of the 

 carapace. 

 10 



