PENAEIDAE. 



269 



Later Protozoaea forms (Fig. 123 A) which Glaus (jSTo. 8) 

 observed are chiefly characterised by the development of five 

 abdominal segments (a^-ctr) still hidden under the larval cuticle, 

 they also show a greater development of the paired eyes and the 

 division of the protopodite of the first antenna {1) into five joints 

 (a feature which recurs in the Protozoaea of Sergestes). The sixth 



Fig. 123. — Later larval stages of Penaeiis (after Claus, from Lang's Text-hook). A, older 

 Protozoaea, dorsal aspect. B, thoraeo-abdominal region of a somewhat older larva with 

 rudiments of limbs, ventral aspect. C, Zoaca, ventral aspect. D, Mysis stage, lateral 

 aspect. 1, 2, first and second antennae; 3, mandible; /,, 5, first and second maxillae; 

 /, II, III, first three maxillipedes ; IV-VIII, first five ambulatory limbs; (IV-VIII), five 

 posterior thoracic segments; {ai-a^), the six abdominal segments ; Ui-a^, the six pleopoda ; 

 cib, abdomen ; en, endopodite ; ex, exopodite ; fr, frontal sensory organ; L, liver ; t, telson. 



abdominal segment is still fused with the telson. Besides the 

 rudiments of limbs already mentioned, the truncated rudiment of 

 the third maxillipede (///) can now be seen. 



The Zoaea which proceeds from the above (Fig. 123 5 and C) 

 is marked by the development of the movable stalked eyes, and 



