2 9 6 



THE CRUSTACEA 



somites defined. The rudiments of the paired eyes appear in the 

 later Protozoea-stage (Fig. 173, D), when also the seventh thoracic 



JF 



PIG. 173. 



Protozoea and Zoea stages of Leucifer. A, first Protozoea-stage. B, maxillula of same. 

 C, maxilla of same. D, later Protozoea-stage (Erichthina, Dana). E, Zoea-stage. a', antennule ; 

 d", antenna ; ab$, uropods ; en, endopodite ; ex, exite ; h, heart ; I, hepatic diverticula ; ind, 

 mandible ; mf-mf"', the three pairs of maxillipeds ; rnp"', somite of third maxillipeds ; mx?, 

 maxillula ; mx", maxilla ; o, paired eye ; oc, nauplius-eye ; ol, labrum ; r, rostrum ; th^-th*, 

 rudiments of fourth to seventh thoracic limbs (first four legs); fl-t 4 , fourth to seventh thoracic 

 somites ; 1-6, abdominal somites. (After Brooks, from Korschelt and Heider's Embryology.), 



somite (the eighth remains undeveloped in the adult Leucifer) and 

 the first four abdominal somites appear. The Zoea-stage (Fig. 173, 

 E) differs from that of Penaeus in the fact that the eyes are not 



