592  ME.  C.  SPENCE  BATE  ON  THE  DEVELOPMENT  OF  DECAPOD  CEDSTACEA. 
But  in  the  larva  of  the  Brachyura  that  we  are  now  describing,  the  carapax  is  seen  to 
pass  distinctly  round  the  base  of  the  eye  and  the  peduncle  to  be  continued  beneath  the 
carapax,  as  in  fig.  B',  Plate  XL.  and  fig.  1,B,  Plate  XL'VT!.,  and  thus  demonstrates  the 
podophthalmic  character  of  the  laiwa  even  in  this  early  stage. 
The  pair  of  appendages  (Plate  XL.  figs.  A and  B,  2)  first  succeeding  the  eyes  repre- 
sent the  anterior  or  upper  antennae.  They  respectively  consist  of  a single  articulation, 
narrowing  towards  the  extremity,  where  are  planted  two  short  simple  hairs,  and  two 
long  almost  invisible  ones  of  the  character  that  I have  elsewhere*  termed  auditori- 
cilia,  since  they  are  only  found  to  exist  upon  the  antennae  which  support  the  acoustic 
organs.  This  fact  enables  us  immediately  to  identify  this  immature  appendage  with 
the  perfected  structure,  even  at  the  earliest  commencement  of  the  young  creatui’e’s  life ; 
and  also  demonstrates  that  the  germ  or  rudiment  of  the  filament,  on  which  part  only 
the  auditory  cilia  are  ever  found,  is  present. 
The  second  pair  of  appendages  (Plate  XL.  fig.  A and  B,  3)  represent  the  second  or 
inferior  antennae,  each  of  which  in  this  stage  consists  of  a basal  articulation  supporting  a 
finely  serrated  spine,  which  is  in  fact  a process  of  the  same ; and  a fiat,  long,  and  squa- 
miform  articulation,  ornamented  at  the  extremity  with  twm  simple  bail’s,  one  longer 
than  the  other.  At  the  base  of  these  two  appendages  may  be  distinguished  a small 
papilla — the  germ  of  the  future  antenna  (3a). 
The  next  succeeding  pair  of  members  are  the  mandibles  (Plate  XL.  fig.  B.  4).  These 
differ  from  the  adult  organs  in  the  absence  of  the  appendage  and  the  internal  lever  pro- 
cesses. In  general  form  they  manifest  a striking  approach  in  their  present  immature 
condition  to  those  of  Talitrus  among  Amphipoda  (Plate  XLVI.  fig.  4 Q). 
Posterior  to  these  succeed  the  first  pair  of  maxillse  (Plate  XL.  fig.  B,  5),  which  consist 
of  three  squamiform  plates,  corresponding  ivith  those  found  in  the  adult,  each  capped 
with  ciliated  hairs,  numbering  about  five  or  six  upon  the  central  or  larger  plate.  These 
are  stouter  than  on  the  other  two,  and  approximate  wfith  increasing  age  more  and  more 
to  the  character  of  spines.  They  also  increase  in  number. 
The  second  pair  of  maxillae  (Plate  XL.  fig.  B,  6)  succeed  immediately  in  position  to  the 
first,  and  in  the  earliest  stage  are  developed  upon  the  type  of  those  of  the  adult.  Each 
of  them  consists  of  three  squamiform  plates,  equally  divided  at  the  apex,  and  fringed 
with  plumose  cilia.  The  plates  are  more  uniformly  equal  than  in  the  adult.  At  the 
base,  the  plate  which  homologizes  with  the  fiabella  and  branchia  is  present,  and  deve- 
loped into  a form  that  differs  somewhat  from,  but  probably  fulfils  the  piu’pose  of,  an 
outletting  valve  at  the  anterior  extremity  of  the  branchial  chamber,  similar  to  the  same 
organ  in  the  adult. 
The  next  succeeding  pair  of  appendages  should  homologize  with  the  maxillipeds,  but 
these  appear  not  to  be  present  in  this  early  form;  and  those  wdiich  do  follow  are 
evidently,  even  at  the  present  period,  the  immature  form  of  the  first  pair  of  gnathojioda 
(Plate  XL.  figs.  A and  B,  8).  Each  of  these  last  consists  of  a strong  basal  joint,  which 
* Annals  of  Natural  History,  1854! ; Eeport  on  Edriophthalma,  British  Association,  1855. 
