58 



HISTOEY OF CRUSTACEA. 



Chap. YII. 



The youngest Nauplius (fig. 28) is immediately fol- 

 lowed by forms in which a fold of skin runs across the 

 back behind the third pair of feet, and four pairs of 

 stout processes (rudiments of new limbs) sprout forth 

 on the ventral surface. Within the third pair of feet, 

 powerful mandibles are developed. 



Fig. 28.12 



In a subsequent moult the new limbs (maxillae, and 

 anterior and intermediate maxillipedes) come into ac- 

 tion, and in this way the Nauplius becojnes a Zoea 

 (fig. 29), agreeing perfectly with the Zoea of the Crabs 

 in the number of the appendages of the body, although 

 very different in form and mode of locomotion and even 

 in many particulars of internal structure. The chief 



12 j^ig_ 28. Nauplius of a Prawn, magn. 45 diam. 



