280 



CRUSTACEA. 



The last stages of emlDryonic life already distinctly show the seg- 

 mentation of the body characteristic of the Phijllosoma larva. The 

 body falls into three sections, the anterior broadened section being 



still swollen by 

 the food - yolk 

 deposited in it, 

 and carrying 

 antennae, man- 

 dibles, and 

 maxillae. This 

 is followed by 

 a moderately 

 broad region, 

 consisting of 

 the segments 

 which carry the 

 maxillipedes 

 and ambulatory 

 limbs, and be- 

 hind this comes 

 a short narrow 

 abdomen. Be- 

 fore the PhyJJi)- 

 soma leaves its 

 embryonic en- 

 velope, certain 

 processes of de- 

 generation (Fig. 

 129) take place 

 in the body. 

 The second aii- 

 tennae (a") are 

 reduced to 

 simple, u n - 

 branched pro- 

 cesses, and the 

 second maxillae 

 (mx") to short 

 unjointed stumps. The first maxillipede in Scyllarus is altogether 

 lost, while in Palhmrus it is retained in the form of a much reduced 

 vestige. The exopodites of the second and third maxillipedes 



Fig. 129.— Young Phyllosoma of ScyUarus (after Glaus). Only tVie 

 basal joints of some of the limbs are drawn, a', first anten_na^; 

 a", second antenna; d, antennal gland; g, brain; /, liver; md, 

 mandible; mx!, first maxilla; mx!', second maxilla; mf", second 

 maxillipede; m/"', third maxillipede; «, ventr.al chain of ganglia ; 

 00, Nauplius eye; ol, npper lip; p', p", p"', first three ambulatory 

 limbs. 



