

CRUSTACEA. 



limbs, and in a transformation of those already present. The first 

 antenna becomes jointed and develops the rudiment of the accessory 

 flageUum (Fig. 131), as well as the olfactory filaments of the prin- 

 cipal flagellum and the auditory organ in the basal joint. The 

 second antenna also (Fig. 131) becomes jointed, and, in the Phyllo- 

 goma of Scyllarus, already shows indications of the lamellate shape 

 typical of the adult. In the mandible, a palp, at first simple and 

 later three-jointed, develops. The maxillae approach the adult form. 

 The first maxillipede and the fourth and fifth ambulatory limbs 

 now develop, while the penultimate ambulatory limb, as well as the 



second maxilli- 

 pede, develop still 

 further. From the 

 basal joints of the 

 maxillipedes and 

 ambulatory limbs, 

 the branchial 

 rudiments now 

 grow out. The 

 abdomen becomes 

 distinctly seg- 

 mented, and six 

 pairs of rudiments 

 of pleopoda appear 

 on it, the last pair 

 participating in 

 the formation of 

 the caudal fin. 

 Internally, the formation of diverticula loads to the development of 

 the hepatic tubes (/). This, in the PhyUowma of ScyUanu (Fig. 

 L29), is commenced by the development of three pairs of caeca, the 

 middle pair Boon showing secondary ramifications. The PhyUosoma 

 of Valinurun (Fig. 129), on the other hand, shows, from the very 

 beginning, richer ramification of the so-called hepatic tubes. The 



organ! of the circulatory system are already, as GbOBNBAUR has 

 d, of the typical Decapodan character. There is a heart pro- 

 vided with three pairs of ostia, from which the arterial vessels 



sd in a form characteristic of the Decapods (Claus, No. 6). 

 The change of tin* PhyUowma larva into the young Btages of 



the adult form, whieh are considerably smaller than the oldest 

 PhyUosoma^ has nol yet been directly observed. 



Fio, 180. — Young Phyttotoma of Palinurus, shortly before hatching 

 (after Oxa.ua, from Lino's Tat-book). ah, abdomen; L, liver; 

 //-///, aeoond and third maxillipedes; iv-vi, first three ambu- 

 latory limbs, 



