i6o 



CRUSTACEA EUCARIDA DECAPODA 



behind is converted into the Protozoaea (Fig. 107), possessing two 

 pairs of biramous maxillipedes. It should be noted that the 

 maxillae, wliich are foliaceous in the adult, are laid down in this 



Fig. 107.-.-Piotozaea larva of Penevs, sp. x 25. 

 (From Balfour, after F. MilUer. ' 



Fig. 108. — Zoaea larva of Penews, 

 sp. X 25. A, A', 1st and 2ntl 

 antennae ; Ah.G^ 6th abdominal 

 appendage ; Mxp, 2nd maxilli- 

 pede ; 7", 4th-8tli thoracic append- 

 ages (future walking legs). (After 

 F. Miiller.) 



condition in the larva, and this prin- 

 ciple holds good throughout Crus- 

 tacean metamorphosis, viz. that when 

 a limb is foliaceous in the adult it 

 is foliaceous in the larva, and when 

 biramous in the adu.lt it is biramous in the larva. Whilst the 

 rest of the thoracic limbs are still rudimentary, the sixth pair of 

 pleopods are being precociously developed (Fig. 108), being the 

 only precociously formed limbs in the Peneidea, though the abdo- 

 minal segments are fully marked off before the thoracic segments, 

 and so must be considered as precocious in development. When 



