TRANSFORMATION OF ORGANS OF ANIMALS 39 



structure of the parts and their auricular combina- 

 tions. On the claw becoming prehensile, the joint 

 hinge consolidates, the lever 

 thus becoming much stronger 

 and permitting the claw to be p r f 

 used to greater advantage. 1 /, 



It now remains to examine ^^LJ? 4sc 



the appendages situated in 

 front of the maxillipedes, i.e. 

 the appendages of the head. Flo . u .- Astacus fluv iatiiis. 

 In the second maxilla (fig. 1 2) *^^^ a ^. 

 a special transformation may 

 be observed. The coxopodite nathide (Huxley) ' 

 (co.), and the basipodite (ba.), are flat plates ; the 

 endopodite (en.), which is small and undivided, ex- 

 hibits signs of degeneration in its 

 w s ^ size, and in the absence of all 

 articulations. The exopodite, accord- 

 ing to some authorities on the 

 Fio.13. Astacus fluvia- subject, no longer exists, while 



tilts. First left max- & 



iiia (i.s/i): co, coxo- according to others it constitutes 



podite, and ba, basi- 



podite, forming P r, with the epipoditc (the analogous 



protopodite; era, en- L * . 



dopodite (Huxiey). part to that which we regard as 

 representing the gill in the maxillipede), a large 

 peculiarly-shaped blade, the scaphognathide (sc.). 



In the first maxilla (fig. 13), a partial degenera- 

 tion of the organ is very marked : the exopodite and 



1 See J. Demoor, JRecherches sur la Marche des Crustaces (Arch, 

 de Zool. exp. etgen., 2 serie, t. iv., 1891). 



T. List, Bewegungsapparat des Arthropoden, 1. Theil, Astacus 

 Fluviatilis. Morphol. Jahrbuch., xxii. Bd. 3. Heft, 1895. 



