258 



CRUSTACEA. 



Nauplius eye, the projecting upper lip (ol), and a few furcal setae, 

 indicating its posterior end. There is as yet no trace of a shield-like 

 fold. In the anterior region of the body, the three pairs of Nauplius 

 limbs (a', a", md) are inserted. Of these, the first (a') is uniramose ; 

 it consists of five joints and carries swimming setae at its end. The 

 second antenna (a") has a two-jointed protopodite and two swimming 

 rami ; when this appendage is compared with that of other forms, we 

 are inclined, in opposition to BROOKS, to regard the ramus, which has 

 several joints and is provided with setae, as the exopodite and the 

 simpler, unjointed branch as the endopodite. The third pair of 

 limbs (mandibles) resembles the second in structure, but is smaller 

 and less jointed. It has an unsegmented protopodite, a single-jointed 



FIG. 118. Two Metanauplius stages of Lucifer (after BROOKS). A, larva just hatched. B, 

 somewhat older stage, a', first antenna ; a", second antenna ; d, shell-fold ; md, mandible ; 

 mx, first maxilla ; mx", second maxilla ; mf, first maxillipede : ol, upper lip ; p, paragnatha. 



endopodite, and an exopodite consisting of three joints, both rami 

 carry a few swimming setae. Following these posteriorly are four 

 pairs of swellings, which represent the rudiments of the two pairs 

 of maxillae (mx', mx") and the first and second pairs of maxillipedes. 

 Later Metanauplius stages (Fig. 118 B), in which the Nauplius 

 limbs show a slight degeneration, have at the sides of the body 

 the rudiment of a shield-like fold (d), and besides this, on the basal 

 joint of the mandible, a stiff masticatory process. 



The Protozoaea stages which now follow show the seven anterior 

 pairs of limbs characteristic of the Zoaea stage completely developed 

 and functional. The anterior part of the body is covered by a dorsal 

 shield which is continued anteriorly above the Nauplius eye into a 



