CHAP. VII. 



DEVELOPMENT OF PENEUS. 



59 



organs of motion are still the two anterior pairs of feet, 

 which are slender and furnished with long setse ; the 

 third pair of feet loses its branches, and becomes con- 

 verted into mandibles destitute of palpi. The labrum 

 acquires a spine di- 

 rected forward and 

 of considerable size, 

 which occurs in all 

 the Zoe'ae of allied 

 species. The bira- 

 mose maxillipedes 

 appear to assist but 

 slightly in locomo- 

 tion. The forked tail 

 reminds us rather 

 of the forms occur- 

 ring in the lower 

 Crustacea, especi- 

 ally the Copepoda, 

 than of the spatuli- 

 form caudal plate 

 which characterises 

 the Zoese of Alplieus, 

 Palsemon, Hippolyte, Fig 29 

 and other Prawns, 



of the Hermit Crabs, the Tatuira and the PorceUanse. 

 The heart possesses only one pair of fissures, and has 

 no muscles traversing its interior like trabeculae, whilst 

 in other Zoe'se two pairs of fissures and an interior appa- 



13 Fig. 29. Young Zoea of the same Prawn, magn. 45 diam. 



