Chap. YII. 



DEVELOPMENT OF PENEUS. 



61 



into action, simultaneously with other profound changes, 

 the Zoea passes into the My sis- or Schizopod-form (fig. 31). 

 The antennae cease to serve for locomotion, their place 

 is taken by the thoracic feet, 

 furnished with long setae, and 

 by the long abdomen which just 

 before was laboriously dragged 

 along as a useless burden, but 

 now, with its powerful muscles, 

 jerks the animal through the 

 water in a series of lively jumps. 

 The anterior antennae have lost 

 their long setae, and by the side 

 of the last (fourth) joint, en- 

 dowed with olfactory filaments, 

 there appears a second branch, 

 which is at first of a single joint. 

 The previously multi-articulate 

 outer branch of the posterior 

 antennae has become a simple 

 lamella, the antennal scale of 

 the Prawn ; beside this appears 

 the stump-like rudiment of the 

 flagellum, probably as a new 

 formation, the inner branch dis- 

 appearing entirely. The five 

 new pairs of feet are biramose, 

 the inner branch short and simple, the outer one longer? 

 annulated at the end, furnished with long setae, and 



Fig. 31. 



Fig. 31. Mysis-iorm of the same Prawn, magn. 45 diam. 



