4 8 



THE CRUSTACEA 



separates from the rest at ecdysis to form a protective case known 

 as the ephippium, containing the resting-eggs. 



DEVELOPMENT. 



Excepting the great majority of the Cladocera and a few 

 Conchostraca (Cyclestheria) in which the development is embryonic, 



Fio. 30. 



Larval stages of Apus cancriformis. A, metanauplius, just hatched; B, "second" larval 

 stage ; C, " fourth" larval stage. 1, antennule ; 2, antenna ; 3, mandible ; 4, maxillula ; I-XIII, 

 first thirteen trunk-somites ; f.s, frontal sense-organ ; ,, hepatic diverticula : s carapace 

 (After Clans, from Korschelt and Heider's Embryology.) 



the Branchiopoda have a free-swimming nauplius or metanauplius 

 stage. Some differences exist even in closely allied forms in the 

 stage of development reached at hatching. In the Notostraca 

 (Fig. 30) and Anostraca the larva is a typical metanauplius with 

 an oval body, showing posteriorly the commencing division of 

 several trunk -somites and sometimes rudiments of their appen- 

 dages. The antennules are well developed, but simple. The 

 antennae have a movable masticatory process. The corresponding 



