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DR.  R.  E.  GRANT  ON  THE  ANATOMY  OF  SEPIOLA  VULGARIS, 
also  unusually  large,  and  are  peculiar  in  their  dorsal  position  and  mobility  on  the  back. 
The  body  or  mantle  of  the  specimens  obtained  from  our  coast  measures  generally  about 
six  lines  in  length,  and  as  much  in  breadth  ;  the  head  measures  only  four  lines  in  length, 
and,  from  the  magnitude  of  the  eyes,  is  of  equal  breadth  with  the  body ;  the  arms  are 
of  unequal  lengths,  the  largest  being  about  an  inch  long,  and  the  shortest  about  a  line 
less.  The  first  or  dorsal  pair  of  arms  are  the  shortest ;  the  second  and  fourth  pairs  are 
of  equal  lengths,  and  are  a  httle  longer  than  the  first  pair ;  the  third  pair  are  the  longest. 
This  is  the  order  of  the  comparative  lengths  of  the  arms  most  common  in  the  Nalied 
Cephalopods.  The  third  and  fourth  arms  on  each  side  are  connected  to  each  other  by 
a  musculo-membranous  fold,  which  extends  to  about  a  third  of  their  length,  and  is 
covered  by  the  skin  and  subjacent  coloured  spots.  The  arms,  which  are  allied  to  those 
of  Octopus  in  their  length,  agree  with  those  of  Loligo  in  being  provided  with  numerous 
long  pedunculated  suckers.  The  suckers  are  of  a  globular  form,  and  are  placed  on  long 
thick  conical  muscular  peduncles ;  the  suckers  are  arranged  in  two  irregular  rows  on 
each  arm,  the  bases  of  their  muscular  peduncles  being  in  contact  with  each  other,  and 
placed  alternately  along  the  middle  of  the  arms^  The  general  surface  of  the  body  has 
a  pale  reddish  tint,  and  the  spots,  of  a  very  dark  purple  colour,  rare  and  small,  extend 
over  the  mantle  and  dorsal  surface  of  the  fins,  the  head  and  arms,  and  partially  over 
the  tentacula.  These  spots  are  interspersed  with  a  few  patches  of  a  larger  size,  and  of 
the  same  deep  purple  hue.  On  removing  a  portion  of  the  thick  elastic  epidermis  from 
the  back  or  head  of  this  animal,  it  is  easy  to  perceive  that  the  spots,  which  remain  un- 
injured on  the  surface  of  the  subjacent  skin  and  cellular  tissue  covering  the  muscles, 
are  fiat  hollow  vesicles  containing  a  thin  colourless  fluid,  in  which  are  small  portions  of 
very  dark  coloured  thick  matter,  imperfectly  mixed  with  the  thin  fluid,  and  much  re- 
sembling the  ink  of  the  animal.  There  appear  to  be  a  few  pores  in  the  parietes  of  these 
vesicles,  of  a  dark  colour,  from  which  coloured  matter  can  be  pressed  into  the  cavity  of 
the  vesicle,  and  moved  to  and  fro  in  the  colourless  fluid  without  being  dissolved  by  it. 
These  coloured  vesicles  of  Cephalopoda,  situate  in  a  cellular  soft  tissue  covering  the 
surface  of  the  skin,  occupy  a  place  analogous  to  that  of  the  rete  mucosum,  the  usual  seat 
of  colour. 
The  tentacula,  about  an  inch  and  a  half  in  length,  thin  and  cylindrical  to  near  their 
termination,  where  they  expand  a  little  and  terminate  in  a  point,  proceed  as  in  other 
Decapods  from  between  the  third  and  fourth  arms  on  each  side.  They  take  their  origin 
from  the  outer  and  fore  part  of  the  head,  external  to  all  the  arms  and  to  the  disk  which 
forms  them  by  its  subdivision ;  in  ascending  they  pass  inwards  between  the  bases  of 
the  arms  just  mentioned,  which  are  the  only  two  connected  together  by  a  membrane, 
and  they  thus  appear  to  extend  from  behind  these  arms  and  their  uniting  membrane. 
When  these  two  long  and  slender  tentacula  are  retracted,  they  are  concealed  and  pro- 
tected by  the  folds  as  by  two  sheaths  ;  and  as  none  of  the  other  arms  are  thus  provided 
'  Plate  XI.  fig.  6. 
