CRUSTACEA. 



501 



antennae become much modified in the subsequent metamorphosis. The 

 Nauplius has a single median eye, as in the adult Cypris, and a fully 

 developed alimentary tract. 



The second stage (fig. 234 B), inaugurated by the first moult, is mainly 

 characterized by the appearance of two fresh pairs of appendages, viz. the 

 first pair of maxillae and the first pair of feet ; the second pair of maxillae 

 not being developed till later. The first pair appear as leaf-like curved 



MX' 



FIG. 235. STAGES IN THE DEVELOPMENT OF CYPRIS. (From Claus.) 



A. Fourth stage. B. Fifth stage. 



MX', first maxilla ; MX", and/', second maxilla ; /". first pair of feet ; L. liver. 



plates (Mx 1 ) more or less like Phyllopod appendages (Claus) though at this 

 stage without an exopodite. The first pair of feet (/") terminates in a 

 curved claw and is used for adhering. The mandibles have by this stage 

 fully developed blades, and have practically attained their adult form, con- 

 sisting of a powerful toothed blade and a four-jointed palp. 



During the third and fourth stages the first pair of maxillae acquire 

 their pectinated gill plate (epipodite) and four blades ; and in the fourth 

 stage (fig. 235 A) the second pair of maxillae (Mx") arises, as a pair of 

 curved plates, similar to the first pair of maxillae at their first appearance. 

 The forked tail is indicated during the fourth stage by two bristles. During 

 the fifth stage (fig. 235 B) the number of joints of the first pair of antennae 

 becomes increased, and the posterior maxilke develop a blade and become 



