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  COLLECTIONS 
  FEOM 
  MELANESIA. 
  

  

  almost 
  black), 
  the 
  differences 
  in 
  the 
  extent 
  to 
  which 
  the 
  papillae 
  are 
  

   developed, 
  and 
  the 
  comparatively 
  much 
  greater 
  firmness 
  of 
  the 
  

   integument 
  of 
  the 
  younger 
  specimens 
  help 
  us 
  to 
  understand 
  how 
  it 
  

   is 
  that 
  several 
  different 
  names 
  have 
  been 
  given 
  to 
  this 
  widely 
  dis- 
  

   tributed 
  species. 
  On 
  the 
  other 
  hand, 
  it 
  is 
  well 
  to 
  still 
  bear 
  in 
  mind 
  

   that 
  our 
  knowledge 
  of 
  Holothurian 
  organization 
  is 
  not 
  yet 
  so 
  com- 
  

   plete 
  as 
  to 
  justify 
  us 
  in 
  definitely 
  asserting 
  that 
  fresh 
  differential 
  

   marks 
  do 
  not 
  yet 
  remain 
  to 
  be 
  discovered 
  ; 
  if 
  there 
  are 
  such, 
  the 
  

   series 
  now 
  regarded 
  as 
  single 
  may 
  be 
  shown 
  to 
  contain 
  represen- 
  

   tatives 
  of 
  more 
  than 
  one 
  form. 
  

  

  As 
  the 
  only 
  illustration 
  of 
  the 
  spicules 
  appears 
  to 
  be 
  that 
  which 
  

   has 
  been 
  given 
  by 
  Prof. 
  Semper, 
  I 
  have 
  had 
  views 
  made 
  of 
  them 
  

   from 
  the 
  side 
  to 
  show 
  the 
  characters 
  of 
  the 
  free 
  projecting 
  processes, 
  

   and 
  from 
  below 
  showing 
  the 
  inside 
  of 
  the 
  hemisphere. 
  

  

  Port 
  Molle; 
  Port 
  Denison 
  ; 
  Torres 
  Straits; 
  Alert 
  Island 
  (Torres 
  

   Straits), 
  17 
  fms., 
  sand. 
  

  

  6. 
  ColocMrus 
  australis. 
  

   Ludwig, 
  Semper''s 
  Arheiten, 
  ii. 
  p. 
  SS, 
  

  

  This 
  species, 
  which 
  is 
  represented 
  by 
  only 
  one 
  specimen 
  from 
  Port 
  

   Molle 
  (14 
  fms.), 
  was 
  more 
  richly 
  so 
  in 
  a 
  collection 
  forwarded 
  some 
  

   three 
  years 
  ago 
  from 
  Port 
  Jackson 
  by 
  Mr. 
  J. 
  Erazier. 
  I 
  do 
  not, 
  

   however, 
  find 
  that 
  the 
  suckers 
  are 
  in 
  them 
  brown 
  in 
  colour, 
  while 
  

   the 
  tentacles 
  are 
  rather 
  black 
  and 
  white 
  than 
  brown 
  and 
  yellow. 
  

   Neither 
  of 
  these 
  are, 
  however, 
  points 
  of 
  any 
  real 
  importance. 
  I 
  

   find, 
  from 
  Mr. 
  Eamsay's 
  collections, 
  that 
  this 
  species 
  is 
  very 
  abundant 
  

   in 
  Port 
  Jackson. 
  

  

  7. 
  Actinocucumis 
  difficilis. 
  (Plate 
  IX. 
  fig. 
  C.) 
  

  

  I 
  have 
  had 
  the 
  greatest 
  difficulty 
  in 
  assuring 
  myself 
  of 
  the 
  specific 
  

   distinctness 
  of 
  this 
  form 
  from 
  the 
  A. 
  typiea 
  of 
  Ludwig, 
  the 
  varia- 
  

   tions 
  exhibited 
  in 
  the 
  present 
  collection 
  impressing 
  one 
  with 
  the 
  

   necessity 
  of 
  the 
  greatest 
  care 
  in 
  the 
  delimitation 
  of 
  species. 
  

  

  The 
  species 
  may 
  perhaps 
  be 
  most 
  conveniently 
  described 
  by 
  

   pointing 
  out 
  the 
  several 
  characters 
  by 
  which 
  it 
  is 
  to 
  be 
  distinguished 
  

   from 
  A. 
  tyjnca. 
  The 
  ambulacral 
  papilhe 
  on 
  the 
  dorsal 
  surface 
  are 
  

   rare, 
  and 
  the 
  suckers 
  are 
  not 
  in 
  more 
  than 
  four 
  rows 
  for 
  each 
  ray 
  ; 
  

   the 
  difterences 
  in 
  the 
  form 
  of 
  the 
  spicules 
  will 
  be 
  best 
  seen 
  by 
  com- 
  

   paring 
  the 
  figures 
  now 
  given 
  with 
  those 
  drawn 
  by 
  Professor 
  Ludwig. 
  

   The 
  retractors 
  are 
  inserted 
  rather 
  further 
  back, 
  being 
  found 
  at 
  24 
  

   miUim. 
  from 
  the 
  anterior 
  end 
  in 
  a 
  specimen 
  65 
  millim. 
  long, 
  and 
  

   at 
  22 
  millim. 
  in 
  one 
  70 
  millim. 
  long 
  ; 
  the 
  genital 
  tubes 
  are 
  shorter 
  

   than 
  in 
  A. 
  ti/pica, 
  being 
  not 
  more 
  than 
  15 
  millim. 
  long 
  in 
  any 
  speci- 
  

   men 
  examined. 
  The 
  Polian 
  vesicle 
  would 
  also 
  appear 
  to 
  be 
  shorter, 
  

   being 
  only 
  7"0 
  miUim. 
  long 
  in 
  a 
  specimen 
  of 
  65 
  millim. 
  length. 
  It 
  

   may 
  be 
  added 
  that 
  the 
  loop 
  of 
  the 
  intestine 
  is 
  exceedingly 
  short 
  ; 
  

   that 
  the 
  tentacles, 
  which 
  are 
  not 
  always 
  20, 
  sometimes 
  seem 
  to 
  

  

  