THE CRAYFISH AND ARTHROPODS IN GENERAL 



231 



ample, upon hatching (Fig. 124) resembles a less specialized 

 prawn-like crustacean, called My sis (Fig. 125), and is said to be 

 in the My sis stage. The shrimp, Penceus, passes through a 

 number of interesting stages before the adult condition is 



FIG. 127. Two later stages in the development of Penaus. A, Zoaa stage ; 

 B, My sis stage. (From Korschelt and Heider after Glaus.) 



attained. It hatches as a larva, termed a Nauplius (Fig. 126, A), 

 possessing a frontal eye and three pairs of appendages (A', A" , 

 Mdf.); this Nauplius molts and grows into a Protozo&a stage 

 (Fig. 126, B) which bears three more pairs of appendages and 

 the rudiments of segments III-VIII. The Protozoaea stage 



