FUNCTIONS  OF  THE  HAIES  OF  THE  CEUSTACEA. 
899 
If  this  supposition  be  correct,  the  chitinogenous  layer  of  M.  Hackel  could  not  be 
the  only  medium  of  communication  between  the  hairs  and  the  internal  parts.  The 
author  had  satisfied  himself  before  the  appearance  of  M.  Hackee’s  paper  on  the  subject, 
that  the  inner  vascular  and  nervous  pulp  sent  prolongations  into  the  hairs,  and  he  had 
too,  even  in  the  Lobster,  seen  indications  of  arrangement  of  the  pulp  which  conveyed  to 
him  the  impression  that  it  was  formed  with  reference  to  the  hairs,  rather  than  that  the 
hairs  were  mere  appendages  to  it.  He  was  anxious  naturally  to  ascertain  in  how  far 
this  view  was  correct. 
In  the  larger  Crustacea,  however,  the  pulp  is  for  the  most  part  too  thick  and  opaque 
to  admit  of  examination  in  its  entire  state,  and  too  soft  to  admit  of  section  without 
destruction  to  its  characters.  But  in  some  of  the  smaller  ones,  as,  for  example,  in  the 
Shrimp,  the  mode  of  arrangement  of  the  inner  soft  layers  can,  with  a little  precaution,  be 
readily  seen.  In  examining  the  tissues  in  these  animals,  a confirmation  of  the  views 
ah’eady  advanced  in  this  paper  will  be  found  in  the  presence  of  an  arrangement  of 
structure  so  remarkable  as  to  require  special  description. 
The  flabellum  on  which  the  eye  appears  to  rest,  is  perhaps  the  situation  in  which 
this  arrangement  can  be  most  easily  demonstrated.  If  the  shell  be  carefully  stripped 
away  from  the  contained  pulp,  the  chitinous  investment  of  the  hairs  will  be  removed 
with  it,  while  then-  contents  will  be  drawn  out  from  their  canals  and  will  remain  in 
connexion  with  the  pulp.  It  will  be  seen,  on  examining  the  pulp,  that  it  is  composed 
of  an  extremely  delicate  chitinous  lamina,  which  supports  the  fibrous  and  cellular 
structure  of  the  chorium,  and  which  is  connected  with  the  tubes  to  be  presently 
described. 
Through  the  centre  from  behind  forwards,  the  chorium  forms  a more  dense  mass 
(fig.  3 a),  in  which  lie  the  nerves  and  principal  vessels.  The  outer  side  is  continued 
fonvards  in  a small  cone-shaped  process  (b),  which  corresponds  to  a similar  process  of 
the  shell,  and  may  be  traced  for  some  distance  towards  the  base  of  the  organ.  At  the 
inner  and  anterior  part,  hes  a series  of  tubes  which  radiate  forwards  from  the  denser 
central  mass.  These  tubes  appear  to  be  composed  of  firm  chitinous  sheaths,  covered 
externally  by  the  epidermic  or  chitinogenous  layer  of  Hackel.  At  their  outer  ends 
they  are  somewhat  contracted  (fig.  4);  at  their  inner  end,  towards  the  anterior  part  of  the 
organ,  they  appear  to  merge  into  the  general  cellular  mass  of  the  chorium ; but  more 
towards  its  base  they  are  truncated,  and  their  terminations  are  clearly  defined  (fig.  3 d). 
Projecting  from  their  outer  ends  are  seen  fibres,  which  correspond  to,  and  have  been 
drawn  from,  the  hairs  (fig.  3 c).  These  fibres  can  be  traced  through  the  whole  length  of 
the  tubes ; but  towards  the  inner  truncated  end  of  the  tubes  they  are  usually  lost  in  the 
cellular  mass  of  the  chorium,  though  sometimes  they  appear  as  projecting  fibres  when 
the  tubes  are  tom  away  from  the  parts  with  which  they  were  connected. 
The  fibres  in  the  flabellum  seem  to  consist  of  an  outer  pellucid  tubular  coat,  with 
contents  of  a more  opaque  character  (fig.  4).  At  their  outer  free  ends,  which  project 
from  the  tubes,  the  fibres  assume  various  characters,  in  accordance  with  the  form  of  the 
