riJNCTIONS  or  the  haies  of  the  ceustacea. 
901 
The  position  of  the  hairs  on  each  side  of  a lamina  to  which  the  pollex  is  opposed,  is 
precisely  analogous  to  that  of  the  hairs  in  the  claw  of  the  Lobster,  where  they  are  placed, 
not  upon,  but  to  the  sides  of  the  tubercles,  and  are  thus  protected  from  the  direct  force 
of  the  opposing  claws. 
The  author  has  been  unwilling  to  multiply  examples,  and  he  conceives  that  enough 
has  been  brought  forward  to  prove  that  the  hairs  of  the  Crustacea  are  in  intimate  rela- 
tion vdth  the  deep  layer  of  the  inner  integument  in  which  the  nerves  terminate,  and  not 
with  the  epidermic  or  chitinogenous  layer  only ; that  the  structure  of  this  integument 
is  in  many  instances  arranged  entirely  with  reference  to  its  connexion  with  the  hairs ; 
that  the  hairs  cannot  therefore  be  regarded  as  prolongations  of  the  shell,  but  as  pro- 
longations of  the  chorium  protected  by  a special  chitinous  investment ; and  finally,  that 
although  many  other  ofiices  are  performed  by  them,  yet  that  their  relation  to  the  cho- 
rium justifies  the  conclusion  that  they  correspond  to  the  papillae  of  the  skin  in  the 
higher  animals,  and  that  they  are  organs  of  general  or  special  sensibility. 
Appendix. 
Since  this  paper  was  communicated  to  the  Society,  the  author  has  found  in  parts  of 
the  Prawn  a more  direct  confirmation  of  his  views  as  to  the  connexion  of  the  nerves  with 
the  hairs  than  he  had  previously  seen. 
In  the  flabella  of  the  tail  of  the  smaller  Prawns  the  shell  is  so  thin,  and  so  nearly 
homogeneous  in  structure,  that  the  soft  textures  within  can  be  seen  perfectly  through  it. 
The  chorium  presents  an  appearance  of  tubular  structure  radiating  towards  the  hairs, 
like  that  which  has  been  described  in  the  Shrimp ; but  the  tubules  are  far  less  clearly 
defined  (fig.  8),  and  do  not  appear  to  possess  a chitinous  basis.  Bands  or  fibres  can  be 
seen  passing  from  the  extremities  of  the  tubules  into  the  hairs.  These  fibres,  however, 
which  are  very  delicate  and  contain  no  chitine,  cannot  be  traced,  as  is  the  case  in  the 
Shrimp,  far  into  the  tubular  structure.  They  appear  rather  to  lose  themselves  towards 
the  outer  margin  of  the  tubular  chorium,  which,  instead  of  presenting  distinct  orifices, 
has  a granular  or  cellular-looking  boundary.  The  nerve  (fig.  7 d)  can  be  seen  entering 
the  flabellum  at  its  base  as  a large  cord,  which  soon  subdivides  and  ultimately  breaks 
up  into  fibres,  which  can  be  traced  into  the  tubules,  and  appear  to  be  continued  on  to 
the  margin  of  the  chorium.  Some  of  these  filaments  seem  to  terminate  in  the  cellular 
boimdary,  while  others  pass  on  to  the  bands  or  fibres  which  go  to  the  hairs. 
Although  the  sheaths  and  fibres  of  chitine  which  have  been  described  in  the  Shrimp 
are  not  found  in  the  Prawn,  yet  in  the  flabelliform  processes  of  some  of  the  larger 
prawns  the  author  has  found  elongated  and  extremely  delicate  chitinous  fibres,  extend- 
ing from  the  inner  part  of  the  tubular  layer  towards  the  roots  of  the  hairs.  They  do 
not  appear  to  be  so  directly  connected  with  the  hairs  as  those  which  exist  in  the  Shrimp, 
and  may  perhaps  serve  the  purpose  of  the  delicate  chitinous  lamina  which  in  the  Shrimp 
gives  support  to  the  chorium  and  to  the  tubular  structure. 
