﻿94 
  Mr. 
  A. 
  Dendy 
  on 
  Sponges 
  from 
  

  

  rounded 
  off 
  at 
  the 
  base 
  (or 
  becoming 
  tylostylote), 
  and 
  very 
  

   gradually 
  sharp-pointed 
  at 
  the 
  apex 
  ; 
  size 
  when 
  full-grown 
  

   about 
  1*2 
  by 
  0*011 
  millim. 
  There 
  are 
  also 
  a 
  few 
  cylindrical 
  

   forms 
  (strongyla) 
  (fig. 
  6, 
  d) 
  and 
  still 
  fewer 
  oxea 
  (fig. 
  6, 
  a); 
  

   but 
  these 
  are 
  probably 
  only 
  abnormal 
  developments 
  of 
  the 
  

   short 
  stout 
  styli 
  such 
  as 
  are 
  frequently 
  found 
  in 
  Axinellids. 
  

  

  There 
  are 
  three 
  dry 
  specimens 
  of 
  this 
  sponge 
  and 
  a 
  piece 
  

   in 
  spirit. 
  

  

  CERATOSA. 
  

  

  Spongionella 
  nigra, 
  n. 
  sp. 
  

  

  Sponge 
  sessile, 
  consisting 
  of 
  a 
  number 
  of 
  vertical 
  lamella?, 
  

   branching 
  and 
  anastomosing 
  with 
  one 
  another 
  often 
  in 
  a 
  very 
  

   complex 
  manner. 
  The 
  largest 
  of 
  the 
  four 
  dry 
  specimens 
  is 
  

   about 
  250 
  millim. 
  high 
  and 
  the 
  same 
  in 
  breadth, 
  and 
  the 
  

   thickness 
  of 
  the 
  lamella? 
  is 
  about 
  5 
  millim. 
  The 
  colour 
  of 
  

   the 
  living 
  sponge 
  is 
  black, 
  when 
  dry 
  dull 
  black, 
  and 
  in 
  spirit 
  

   rather 
  lighter 
  blackish 
  grey. 
  Texture 
  tough 
  and 
  resilient. 
  

   Surface 
  (dry 
  and 
  in 
  spirit) 
  granulated. 
  The 
  oscula 
  are 
  

   abundantly 
  scattered, 
  usually 
  on 
  the 
  inwardly 
  turned 
  surfaces 
  

   of 
  the 
  lamella?, 
  and 
  almost 
  or 
  quite 
  confined 
  to 
  one 
  surface 
  

   of 
  each 
  lamella 
  ; 
  they 
  are 
  about 
  1-2 
  millim. 
  in 
  diameter 
  and 
  

   are 
  compound, 
  each 
  consisting 
  of 
  an 
  aggregation 
  of 
  several 
  

   smaller 
  ones. 
  

  

  The 
  dermal 
  skeleton 
  is 
  a 
  well-developed 
  but 
  irregular 
  net- 
  

   work 
  of 
  horny 
  fibre 
  with 
  fairly 
  wide 
  polygonal 
  meshes 
  ; 
  the 
  

   fibres 
  averaging 
  about 
  - 
  02 
  millim. 
  in 
  diameter. 
  

  

  The 
  main 
  skeleton 
  is 
  a 
  rectangularly 
  meshed 
  network 
  of 
  

   very 
  distinct 
  primary 
  and 
  secondary 
  fibres 
  ; 
  the 
  primary 
  

   fibres 
  average 
  about 
  0'049 
  millim. 
  in 
  diameter 
  and 
  the 
  secon- 
  

   daries 
  about 
  half 
  as 
  much. 
  

  

  All 
  the 
  fibres 
  of 
  the 
  skeleton 
  are 
  composed 
  of 
  pale-coloured 
  

   spongin 
  without 
  any 
  trace 
  of 
  foreign 
  enclosures. 
  The 
  fibres 
  

   are 
  solid, 
  and 
  it 
  is 
  difficult 
  to 
  make 
  out 
  any 
  distinct 
  central 
  

   granular 
  core, 
  though 
  possibly 
  such 
  may 
  exist, 
  at 
  any 
  rate 
  in 
  

   some 
  cases. 
  

  

  The 
  ectosome 
  is 
  represented 
  by 
  the 
  thin 
  dermal 
  membrane. 
  

   The 
  choanosome 
  is 
  very 
  delicate 
  and 
  gelatinous, 
  containing 
  a 
  

   large 
  number 
  of 
  amoeboid 
  and 
  stellate 
  cells. 
  The 
  canal- 
  

   system 
  is 
  eminently 
  lacunar 
  and 
  the 
  lacuna? 
  are 
  very 
  strongly 
  

   developed. 
  The 
  flagellated 
  chambers 
  are 
  irregularly 
  sac- 
  

   shaped 
  and 
  they 
  vary 
  much 
  in 
  size, 
  the 
  full-grown 
  chambers 
  

   averaging 
  about 
  0*07 
  millim. 
  in 
  diameter. 
  They 
  are 
  not 
  

   placed 
  very 
  close 
  together 
  and 
  lie 
  irregularly 
  scattered 
  through 
  

  

  