﻿the 
  Gulf 
  of 
  Manaar. 
  95 
  

  

  the 
  choanosome, 
  so 
  as 
  to 
  leave 
  frequent 
  wide 
  interspaces 
  

   devoid 
  of 
  chambers. 
  They 
  open 
  directly 
  into 
  the 
  excurrent 
  

   lacunae. 
  

  

  This 
  is 
  a 
  very 
  remarkable 
  and 
  interesting 
  species, 
  one 
  of 
  

   the 
  most 
  striking 
  features 
  of 
  which 
  is 
  the 
  large 
  size 
  of 
  the 
  

   flagellated 
  chambers. 
  These 
  chambers 
  are 
  conspicuous 
  objects 
  

   even 
  in 
  unstained, 
  hand-cut, 
  rough 
  preparations 
  of 
  ordinary 
  

   spirit 
  material. 
  

  

  The 
  genus 
  was 
  founded 
  by 
  Bowerbank 
  for 
  his 
  Spongio- 
  

   nella 
  pulchella, 
  a 
  British 
  species*, 
  and 
  he 
  afterwards 
  describedf 
  

   another 
  species, 
  S. 
  Holdsworthii, 
  from 
  the 
  Ceylon 
  Pearl 
  

   Banks. 
  All 
  his 
  specimens 
  of 
  the 
  genus 
  appear 
  to 
  have 
  been 
  

   dry, 
  and 
  I 
  am 
  now 
  able, 
  from 
  my 
  examination 
  of 
  the 
  spirit- 
  

   preserved 
  material 
  sent 
  by 
  Mr. 
  Thurston, 
  to 
  amend 
  his 
  

   original 
  diagnosis 
  as 
  follows 
  : 
  — 
  " 
  Genus 
  Spongionella, 
  Bower- 
  

   bank. 
  Sponge 
  consisting 
  of 
  flattened 
  lamellas. 
  Main 
  skele- 
  

   ton 
  of 
  very 
  distinct 
  primary 
  and 
  secondary 
  fibres 
  without 
  

   foreign 
  enclosures, 
  arranged 
  so 
  as 
  to 
  leave 
  rectangular 
  meshes. 
  

   Ectosome 
  a 
  thin 
  dermal 
  membrane. 
  Choanosome 
  extremely 
  

   delicate, 
  transparent 
  and 
  gelatinous. 
  Canal-system 
  lacunar. 
  

   Flagellated 
  chambers 
  very 
  large, 
  irregularly 
  sac-shaped, 
  

   opening 
  directly 
  into 
  the 
  excurrent 
  lacunas." 
  

  

  The 
  genus 
  possibly 
  finds 
  its 
  nearest 
  ally 
  in 
  Spongelia, 
  and 
  

   would 
  fall 
  under 
  Lendenfeld's 
  subfamily 
  SpongelinEe 
  J. 
  It 
  

   presents, 
  however, 
  very 
  striking 
  resemblances 
  to 
  the 
  Chali- 
  

   ninae. 
  These 
  resemblances 
  are 
  most 
  apparent 
  in 
  the 
  general 
  

   external 
  form 
  and 
  in 
  the 
  structure 
  and 
  arrangement 
  of 
  the 
  

   horny 
  fibres 
  (except 
  of 
  course 
  as 
  regards 
  the 
  total 
  absence 
  of 
  

   spicules). 
  The 
  histological 
  character 
  of 
  the 
  choanosome 
  also 
  

   agi'ees 
  with 
  that 
  found 
  in 
  Chalinina? 
  § 
  ; 
  but 
  the 
  flagellated 
  

   chambers 
  are 
  very 
  much 
  larger, 
  and 
  this 
  would 
  appear 
  to 
  be 
  

   an 
  important 
  distinction 
  ||. 
  

  

  According 
  to 
  Vosmaer 
  ^J 
  Bowerbank's 
  Spongionella 
  is 
  

   synonymous 
  with 
  Schmidt's 
  Gacospongla. 
  This 
  is 
  a 
  difficult 
  

   question, 
  and 
  in 
  order 
  to 
  settle 
  it 
  we 
  require 
  a 
  much 
  more 
  

   extensive 
  knowledge 
  of 
  the 
  anatomy 
  of 
  these 
  forms. 
  Ac- 
  

   cording 
  to 
  Lendenfeld 
  ** 
  Gacospongla 
  is 
  one 
  of 
  those 
  forms 
  

  

  * 
  Vide 
  Mon. 
  Brit. 
  Spong. 
  vol. 
  i. 
  pi. 
  xxxvii. 
  fig. 
  380, 
  vol. 
  ii. 
  pp. 
  12, 
  359, 
  

   vol. 
  iii. 
  pi. 
  lxv. 
  

  

  t 
  Proc. 
  Zool. 
  Soc. 
  Lond. 
  1873, 
  p. 
  25. 
  

  

  \ 
  Vide 
  Proc. 
  Zool. 
  Soc. 
  Lond. 
  1886, 
  p. 
  589. 
  

  

  § 
  Vide 
  Lendenfeld, 
  ' 
  Zoologiscbe 
  Jabrbiicher,' 
  Band 
  ii. 
  p. 
  734. 
  

  

  || 
  Vide 
  Lendenfeld, 
  loc. 
  cit. 
  ; 
  also 
  Bendy, 
  Proc. 
  Zool. 
  Soc. 
  Loud. 
  1887, 
  

   p. 
  526. 
  

  

  ^[ 
  " 
  Porifera," 
  in 
  Bronn's 
  Klass. 
  und 
  Ordnuug. 
  des 
  Thierreiclis, 
  p. 
  364. 
  

  

  ** 
  Proc. 
  Zool. 
  Soc. 
  Lond. 
  1880, 
  p. 
  587. 
  

  

  