254 



CRUSTACEA. 



fold covering the lateral parts of the posterior limb-rudiments. The 

 posterior end of the body, below the anal aperture which is now 

 becoming more distinct, is lengthened into two rounded furcal 

 processes fringed with setae. Later Metanauplius stages show a 

 change in the third limb, which has entirely lost the form of 



FIG. 117. Three stages of development of Euphuusia (from LANG'S Text-book). A, Meta- 

 nauplius (after METSCHNIKOFF). B, Calyptopis (after GLAUS). 6', older Calyptopis (after 

 GLAUS). 1 and 3, first and second antennae ; 3, mandible ; It, 5, first and second maxillae ; 

 /, first pair of maxillipedes ; ab, abdomen ; (a 1 -a s ) first five abdominal segments ; a 6 , 

 sixth pair of pleopoda ; an, anus ; fs, frontal sensory organ ; o, upper lip ; u, paragnatha ; 

 th, thoracic segments. 



a swimming appendage and has developed into a masticatory blade 

 (mandible) with a greatly reduced palp. The shield-like fold has 

 now developed in the anterior region of the body, and thus 

 surrounds the cephalic portion of the larva (cf. the later stages, 

 Fig. 117 B and C). In the posterior limbs, the first indication of 



