GAMMARrs. 335 



peduncle or protopodite bearing a stout many-jointed 

 nagellum, which may correspond to the endopodite, and 

 which is about the length of the last two joints of the 

 peduncle combined. This nagellum bears a number of 

 setae, some being plumose, as well as two spines, on each 

 segment. In addition, on the upper margin of the distal 

 end of each segment is a calceolus (PL I., fig. 3, calc). 

 This is a cup-shaped, stalked projection, with a beaded 

 rim, within the body of which may be distinguished a 

 darker, curved mass, which Blanc (2) considers may be a 

 sensoiy nerve mass. Since, contrary to the belief of 

 earlier observers, calceoli are present on the antennse of 

 females as well as males in G. pulex (though apparently 

 absent in female G. locusta), Blanc (2) thinks they are 

 probably organs of hearing rather than of smelling or 

 clasping. Observations of the behaviour of the antennae 

 during the chiming of a bell do not confirm this. The 

 first joint of the second antenna is enlarged and fits into 

 a notch in the cephalic ring. On its ventral surface it 

 bears the antennary cone (PI. I., fig. 2, ant. c; PL II., 

 ant. c), on the pointed apex of which opens the duct of 

 the excretory organ, which occupies the basal joint of the 

 antenna. 



The mandibles (PL I., fig. 4) each consist of a strong 

 undivided protopodite bearing two jaws armed with 

 double rows of saw-like teeth (PL I., fig. 4, mn. t.) and 

 furnished in front and at the sides with scooplike pro- 

 jections, which occupy the deep sinus between the lateral 

 corners of the cephalic shield (PL II.) and apparently aid 

 in holding up the food between the saw-like jaws. Each 

 mandible is provided with a three-jointed mandibular 

 palp, which is probably the endopodite, and is armed with 

 slanting rows of setae, projecting in three planes at right 

 angles to one another (PL I., fig. 4, mn. p.). 



