LOBSTER. 67 



Raise the branchiostegites and see 



beneath them the gills. 



2. A jointed flexible posterior part, the abdo- 

 men. 



Count the number of segments. In what 

 plane or planes can the abdomen be 

 moved ? 

 HI. Appendages. 



Jointed limbs attached to the ventral aspect of 

 the body. (To be studied in detail later 

 (0. II.) ). 

 IV. External Openings. 



1. The slit-like auditory openings : on the flat 



upper surface of the basal segments of the 

 antennules. 



2. The excretory openings, perforating a tuber- 



cle on the ventral side of the basal segment 

 of each antenna. 



3. The mouth, in the median line, seen by 



pushing apart the appendages on the ven- 

 tral side of the head. 



4. The genital openings : 



(a) In the female : on the basal segment 



(coxopodite) of the second from the 

 last thoracic appendage. 



(b) In the male . on the basal segment of 



the posterior thoracic appendage. 



5. The anus : a slit on the ventral surface of the 



posterior abdominal segment. 



