﻿SPONGIIDA. 
  475 
  

  

  simply 
  grey. 
  A 
  distinct 
  cortical 
  layer, 
  containing 
  the 
  subcortical 
  

   crypts, 
  and 
  formed 
  in 
  adult 
  specimens 
  by 
  the 
  space 
  between 
  the 
  

   heads 
  of 
  the 
  zonc-spicules 
  and 
  those 
  of 
  the 
  anchors, 
  diameter 
  about 
  

   ■7 
  millim. 
  ; 
  sarcode 
  here 
  of 
  same 
  consistency 
  as 
  in 
  rest 
  of 
  sponge. 
  

   Sponge-sarcode 
  below 
  surface 
  rather 
  dark 
  yellow-brown, 
  rather 
  

   granular; 
  that 
  of 
  surface 
  (in 
  well-preserved 
  specimens) 
  reddish 
  

   brown, 
  granular. 
  

  

  Spicules 
  : 
  — 
  (1) 
  Zone-spicule, 
  with 
  long 
  shaft 
  tapering 
  gradually 
  

   from 
  head 
  to 
  sharp 
  point 
  ; 
  head 
  composed 
  of 
  three 
  bifid 
  arms 
  ; 
  the 
  

   proximal 
  third 
  of 
  each 
  arm 
  projects 
  forward 
  at 
  an 
  angle 
  of 
  about 
  

   120° 
  to 
  the 
  shaft, 
  and 
  then 
  bifurcates 
  in 
  a 
  plane 
  parallel 
  to 
  that 
  of 
  

   the 
  surface 
  of 
  the 
  sponge, 
  so 
  that 
  the 
  ultimate 
  divisions 
  are 
  parallel 
  

   with 
  this 
  surface 
  ; 
  the 
  ultimate 
  divisions 
  taper 
  gradually 
  to 
  sharp 
  

   points 
  from 
  the 
  point 
  of 
  bifurcation 
  ; 
  shaft 
  about 
  3 
  millim. 
  long 
  by 
  

   •035 
  millim. 
  in 
  diameter 
  ; 
  total 
  length 
  of 
  single 
  arm 
  '32 
  millim., 
  of 
  

   proximal 
  (simple) 
  part 
  •! 
  millim. 
  ; 
  diameter 
  of 
  proximal 
  part 
  

   throughout 
  •028-"032 
  millim., 
  of 
  base 
  of 
  ultimate 
  divisions 
  about 
  

   the 
  same. 
  (2) 
  Anchor, 
  with 
  long 
  shaft 
  tapering 
  gradually 
  from 
  

   head 
  to 
  sharp 
  point, 
  and 
  head 
  composed 
  of 
  three 
  arms 
  tapering 
  

   gradually 
  to 
  sharp 
  points, 
  curved 
  backwards 
  to 
  form 
  angles 
  of 
  about 
  

   45° 
  with 
  shalt 
  (the 
  angles 
  vary 
  slightly 
  in 
  different 
  specimens) 
  ; 
  shaft 
  

   about 
  2-1 
  millim. 
  by 
  '022 
  to 
  -024 
  millim. 
  ; 
  expanse 
  of 
  arms 
  -ll 
  to 
  

   •12 
  millim., 
  diameter 
  of 
  arm 
  at 
  base 
  about 
  -02 
  millim. 
  (3) 
  Body 
  

   acerate, 
  long 
  and 
  slender, 
  smooth, 
  tapering 
  gradually 
  to 
  sharp 
  

   points 
  from 
  the 
  centre 
  ; 
  size 
  about 
  3 
  by 
  '025 
  millim. 
  (4) 
  Flesh- 
  

   spicule, 
  composed 
  of 
  about 
  7 
  to 
  12 
  straight 
  arms, 
  radiating 
  from 
  a 
  

   centre 
  which 
  does 
  not 
  show 
  any 
  perceptible 
  inflation 
  ; 
  arms 
  very 
  

   slender 
  (about 
  -0008 
  millim. 
  in 
  diameter), 
  terminated 
  by 
  heads 
  of 
  

   about 
  twice 
  their 
  own 
  diameter 
  ; 
  spicule 
  '01 
  to 
  'OlS 
  millim. 
  in 
  

   diameter 
  across 
  the 
  arms 
  : 
  distributed 
  generally 
  in 
  sarcode. 
  

  

  Hab. 
  Prince 
  of 
  Wales 
  Channel 
  and 
  West 
  Island, 
  Torres 
  Straits, 
  

   7-9 
  fms. 
  ; 
  bottom 
  sand 
  and 
  coral. 
  Arafura 
  Sea, 
  off 
  N.W. 
  coast 
  of 
  

   Australia, 
  32-30 
  fms. 
  ; 
  bottom 
  sand, 
  mud, 
  and 
  shells. 
  

  

  This 
  appears 
  to 
  be 
  a 
  small 
  species, 
  none 
  of 
  the 
  specimens 
  exceed- 
  

   ing 
  13 
  millim. 
  in 
  their 
  longest 
  diameter. 
  It 
  exhibits, 
  as 
  com- 
  

   pared 
  with 
  aS'. 
  pm-purea^ 
  a 
  remarkable 
  constancy 
  in 
  its 
  form 
  and 
  

   in 
  the 
  occurrence 
  of 
  a 
  vent, 
  and 
  the 
  spicules 
  vary 
  but 
  slightly 
  in 
  

   form 
  and 
  dimensions 
  (the 
  only 
  variations 
  observed 
  are 
  incorpo- 
  

   rated 
  with 
  the 
  description 
  above). 
  In 
  Torres 
  Straits 
  very 
  few 
  

   specimens 
  were 
  obtained 
  ; 
  but 
  in 
  the 
  Arafura 
  Sea 
  a 
  considerable 
  

   number 
  of 
  small 
  specimens 
  occurred. 
  Stelletta 
  clavosa 
  differs 
  

   from 
  all 
  nearly 
  allied 
  forms 
  excej)t 
  S. 
  tethyopsis^ 
  Carter, 
  in 
  the 
  

   bifurcation 
  of 
  the 
  arms 
  of 
  the 
  zone-spicule, 
  and 
  from 
  the 
  latter 
  

   species 
  by 
  the 
  absence 
  of 
  " 
  anchors 
  " 
  and 
  of 
  an 
  external 
  as 
  distin- 
  

   guished 
  from 
  an 
  internal 
  form 
  of 
  stellate. 
  The 
  arms 
  of 
  the 
  zone- 
  

   spicule 
  are 
  much 
  longer 
  in 
  proportion 
  to 
  their 
  thickness 
  than 
  in 
  

   Carter's 
  species. 
  

  

  Parasite. 
  In 
  the 
  superficial 
  sarcode 
  (probably 
  just 
  beneath 
  the 
  

   ectoderm) 
  of 
  one 
  specimen 
  occur 
  a 
  large 
  number 
  of 
  a 
  chain-hke 
  

   Alga, 
  resembling 
  Nostoc, 
  usually 
  coiled, 
  with 
  very 
  distinct 
  cells. 
  

  

  