176 ARTHROPOD A 



covered by a tergum. The covering between each pair of 

 pleopods is the sternum, the immovable flap lateral to them 

 is the pleuron. Compare the abdominal appendages or pleo- 

 pods of a male and a female. 



5. The ventral side of the cephalothorax 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 distri- 

 bution 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 

 composed of two segments (coxopod and basipod). The 

 endopod has five pieces {ischipod, meropod, carpopod, pro- 

 pod, and dactylopod). The exopod has two large and many 

 small segments. Attached to the coxopod laterally is an epi- 

 pod which extends 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 scaphognathite, which is made up of both 

 exopod and epipod and which has a special function that 

 should be understood; first maxilla, thin and leaflike; man- 

 dible with two hard rods for the attachment of muscles. 



10. Detach and examine one each of the eyes and first 

 and second antennae. On the flat side of the basal joint of 

 each first antenna note a dark suture — the. scar of the former 

 opening into the statocyst. Do you understand what function 

 is performed by the statocysts? Near the base of the second 

 antenna find the opening of the renal organ (green gland). 



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

 with the third maxilliped. What part, endopod or exopod, 

 is lacking? Which bears forceps or chelae? Note in the 



