300 



CRUSTACEA. 



serves as a swimming organ degenerates and finally altogether 

 disappears. The endopodite of the first maxillipede remains com- 

 paratively small, and gradually develops the rudiment of a small 

 prehensile claw at its end. The endopodite of the second maxillipede, 



on the contrary, early develops into a 

 powerful, clawed raptorial limb. On the 

 basal joints of both these limbs the 

 rounded epipodial plates, which are still 

 without setae, appear simultaneously. 

 The three folloiving pai?s of hiramose 

 limbs meantime undergo an unusually 

 interesting jirocess of degeneration, by 

 which their transformation into the 

 adult form is introduced. Here also 

 the exopodite gradually vanishes, but, 

 in addition, the endopodite becomes an 

 unjointed rudiment without setae, out of 

 which, only in later stages, is produced 

 the adult limb ending in a short pre- 

 hensile claw. Indeed, the degeneration 

 of these three limbs may go so far that 

 they disappear altogether, only to re- 

 appear in later stages simultaneously 

 with the rudiments of limbs of the 

 three following thoracic segments (sixth, 

 seventh, and eighth thoracic segments). 

 In the latter case we have a larva which, 

 in the possession of the seven anterior 

 pairs of limbs and the absence of the 

 six following thoracic limbs, shows a 

 certain agreement with the Zoaea of 

 other Malacostraca, and which has there- 

 fore been called the Pseudozoaea of the 

 Stomatopoda (Fig. 143). This larval 

 type, first described by Fr. Muller, 

 chiefly occurs (Claus) in the larvae 

 belonging to the genera Pseudosquilla 

 and Gonodactylu8 which were described 

 by Brooks as Pseuderichthus and Gonerichthus ; it is, however, 

 found (BROOKS) in the ontogenetic series (Lysioerichthus) of 

 -mis T/yeioaquilla. 



Pro. 11.'. Older Erichthtu (after 



•iais). „', first antenna; a", 

 Mcond antenna; i-V, maxilli- 

 pedes; VI-Vill, rudiments of 

 the three ambulatory limbs ; 

 "'-" ,; , the six pleopoda; br, 

 branchial rudiments. 



