900 
ME.  C.  DE  MiOEGAI^  ON  THE  STErCTUEE  AND 
hairs  to  which  they  belong.  Sometimes  they  are  split  into  two  or  three  branches, 
sometimes  they  present  serrated  margins,  and  at  times  they  hare  a plumose  character, 
from  the  presence  of  secondary  fibres  which  correspond  with  the  plumules  of  the  hairs. 
Hence  it  is  evident,  that  although  in  the  examination  of  the  hairs  none  of  the  contents 
can  be  seen  entering  the  secondary  processes,  yet  that  in  reality  they  do  receive  con- 
tinuations from  the  internal  structures  of  the  hairs. 
The  tubular,  fibre-containing  structure  may  be  found  readily  in  some  of  the  smaller 
maxillary  appendages. 
In  the  terminal  joint  of  the  larger  maxillary  foot  of  the  Shrimp,  in  which  the  hairs 
form  a sort  of  brush  all  around  it,  the  tubes  may  be  seen  clustered  together,  their 
openings  arranged  in  rows  corresponding  to  the  rows  of  hairs,  as  seen  in  figs.  5 and  6. 
But  it  is  not  only  in  parts  which  are  usually  recognized  as  ministering  to  sensation 
that  this  structure  is  found.  The  same  may  be  seen  wherever  the  hahs  are  abundant,  as, 
for  example,  in  the  ambulatory  organs  and  in  the  claw.  In  order  to  show  this  distinctly, 
it  is  necessary,  after  removing  the  shell,  to  pick  away  the  muscles  from  within  the 
chorium,  and  then  the  tubes  and  their  contained  fibres  will  be  at  once  seen. 
In  describing  the  connexion  of  the  hairs  with  the  chorium  in  the  Lobster  and  larger 
Crustacea,  and  the  existence  of  the  mass  of  pulp  largely  supplied  with  nerves  which  is 
contained  in  the  terminal  joints  of  the  claw,  it  was  assumed  that  there  was  an  associ- 
ation between  the  nerves  and  the  hairs.  In  these  larger  animals,  however,  the  author 
could  not  trace  in  a satisfactory  manner  such  a connexion,  though  he  often  saw  bundles 
and  fibres,  which  he  believed  to  be  nerve  tissue  passing  towards  the  hair-tubes. 
In  the  claw  of  the  Shrimp,  however,  the  nerves  can  be  traced  so  dhectly  into  the 
immediate  neighbourhood  of  the  hair-fibres,  as  to  leave  no  room  for  doubt  as  to  their 
relation  to  them.  The  general  structure  is  the  same  as  in  the  Lobster,  but  there  are 
some  peculiarities  which  deserve  special  mention.  The  pollex  and  index  do  not  meet 
so  as  to  resemble  pincers,  but  the  sharp  scythe-shaped  pollex  (fig.  7 a)  folds  down  upon 
the  margin  of  the  metatarsus,  and  merely  touches  with  its  extremity  a small  process 
which  projects  on  the  opposite  side  of  the  metatarsus  (5),  and  which  may  be  con- 
sidered as  an  index.  The  extremity  of  the  metatarsus  to  which  the  pollex  is  applied, 
presents  a thin  central  lamina  (c),  on  each  side  of  which,  and  protected  as  it  were  by 
it,  is  a row  of  very  delicate  hairs.  If  the  chorium  be  carefully  dragged  away  from 
the  shell,  and  the  muscles  drawn  out  from  it,  the  hair-fibres  will  be  found  passing  into 
a tubular  structure  much  like  that  before  described,  while  their  free  extremities  rest  on 
a very  delicate  lamina,  which  is  probably  the  chitinogenous  membrane  of  the  corre- 
sponding lamina  of  the  shell  before  noticed,  and  which  invests  it  on  both  sides.  Run- 
ning into  the  deep  layer  of  the  chorium  in  which  the  hair-fibres  are  imbedded,  is  seen 
a large  nerve  branch  [d),  which  spreads  out  when  it  reaches  this  structure.  The  ulti- 
mate distribution  of  the  nerve  can  as  yet  be  only  surmised,  but  as  the  structure  con- 
nected with  the  fibres  is  the  only  one  in  this  situation,  there  can  be  no  doubt  that  the 
nerve  is  directly  associated  with  them. 
