THE METAMORPHOSIS OF A CRAB. 211 



2. The antennae (Fig. 107, An). These consist of two 

 portions : a spine, which in Callinectes is about as long as 

 the rostrum, and is fringed with short hairs ; and a shorter 

 movable exopodite, or scale, which springs from near the 

 base of the spine, and ends in two slender, tapering hairs. 

 The scale corresponds to the scale at the base of the an- 

 tenna of a lobster or crayfish, and the flagellum of the 

 antenna of the adult crab is absent in the newly hatched 

 zoea. 



3. The labrum (Fig. 108, L). This is a rounded, pro- 

 jecting, hood-like organ, which is usually marked by a 

 conspicuous dendritic pigment spot. Its posterior free 

 edge is fringed with short hairs. 



4. The mandibles (Fig. 108, M ). These are usually 

 marked by pigment spots, and their cutting edges have 

 two or three hook-like points or " teeth." The mandibles 

 are not exactly alike, the left differing from the right a 

 little. The palpus carried by the mandible of the adult 

 is entirely absent in the zoea. 



5. The first maxilla (Fig. 108, Mx 1 ) consists of three 

 portions : a basipodite (b), a coxopodite (ex), and an endo- 

 podite (en). 



The basipodite and coxopodite together make up the 

 long protopodite or body of the maxilla, and their inner 

 edges are fringed with stout plumose hairs. The endopo- 

 dite is more slender, two-jointed, and it ends with a few 

 long slender plumose hairs. 



6. The second maxilla (Fig. 108, Mx 2 ) consists of a 

 protopodite (p), an endopodite (en), and an exopodite or 

 scaphognathite (.sc). The protopodite is made up of a 

 small coxopodite (ex) and a much larger basipodite (6). 

 The free inner ends of these joints are notched or bilobed, 

 and carry long, slender, plumose hairs. The tip of the 



