i6o 



CRUSTACEA EUCARIDA— DECAPODA 



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

 pairs of birainou.s ma. millipedes. It should be noted that the 

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



Fig. 107. — Protozaea larva of Peneus, sp. x 25. 

 (From Balfour, after F. Miiller. 



Fig. 108.— Zoaea larva of Peneus, 

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

 antennae ; Ab.6, 6th abdominal 

 appendage ; Mxp, 2nd maxilli- 

 pede ; T, 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 adult 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 



