﻿10 
  A 
  MONOGRAPH 
  OF 
  THE 
  VICTORIAN 
  SPONGES. 
  

  

  preparations 
  of 
  the 
  siliceous 
  sponge 
  Halichondria 
  panicen* 
  For 
  more 
  detailed 
  

   descriptions 
  and 
  illustrations 
  of 
  this 
  remarkable 
  modification 
  of 
  the 
  collared 
  cells 
  in 
  

   certain 
  sponges 
  I 
  must 
  refer 
  the 
  reader 
  to 
  the 
  writings 
  of 
  Sollas 
  and 
  myself 
  just 
  

   quoted. 
  

  

  Sollas, 
  again, 
  t 
  has 
  pointed 
  out 
  that 
  in 
  the 
  calcareous 
  sponges 
  the 
  collared 
  cells 
  

   are 
  usually, 
  if 
  not 
  ahvays, 
  larger 
  than 
  in 
  other 
  sponges, 
  a 
  statement 
  which 
  is 
  

   supported 
  by 
  my 
  own 
  observations. 
  According 
  to 
  HcBckel, 
  the 
  collared 
  cells 
  in 
  the 
  

   Calcarea 
  range 
  from 
  0*005 
  to 
  O'OOO 
  mm. 
  in 
  diameter, 
  while 
  in 
  the 
  non-calcareous 
  

   sponges 
  Sollas 
  gives 
  the 
  diameter 
  of 
  the 
  collared 
  cells 
  as 
  only 
  0'003 
  mm. 
  

  

  Enough 
  has 
  been 
  said 
  to 
  show 
  that 
  the 
  collared 
  cells 
  are 
  not 
  so 
  uniform 
  in 
  

   structure 
  in 
  all 
  sponges 
  as 
  has 
  generally 
  been 
  supposed, 
  and 
  I 
  must 
  now 
  make 
  a 
  few 
  

   observations 
  on 
  the 
  condition 
  of 
  these 
  elements 
  in 
  the 
  Calcarea 
  Homocoela. 
  

  

  We 
  have 
  seen 
  above 
  that 
  the 
  collared 
  cell 
  is 
  a 
  more 
  or 
  less 
  polymorphic 
  structure, 
  

   and 
  this 
  polymorphism 
  is 
  exhibited 
  mainly 
  in 
  a 
  great 
  readiness 
  to 
  withdraw 
  the 
  

   collar 
  and 
  fiagellum 
  into 
  the 
  protoplasmic 
  body 
  of 
  the 
  cell. 
  The 
  mere 
  act 
  of 
  

   removing 
  a 
  sponge 
  from 
  the 
  water 
  and 
  placing 
  it 
  in 
  alcohol 
  seems, 
  as 
  a 
  rule, 
  to 
  be 
  

   sufficient 
  to 
  cause 
  the 
  total 
  retraction 
  of 
  the 
  collars 
  and 
  flagella, 
  and 
  it 
  is 
  in 
  this 
  

   condition 
  of 
  retraction 
  that 
  the 
  collared 
  cells 
  are 
  generally 
  found 
  in 
  microscopical 
  

   preparations. 
  Even 
  in 
  this 
  state, 
  however, 
  they 
  are 
  readily 
  recognisable. 
  Exactly 
  

   as 
  the 
  ectodermal 
  cells 
  form 
  an 
  epithelial 
  membrane 
  over 
  the 
  outside 
  of 
  the 
  Ascon- 
  

   tube, 
  so 
  the 
  endodermal, 
  collared 
  cells 
  form 
  a 
  continuous 
  epithelium 
  lining 
  the 
  

   inside 
  of 
  the 
  tube. 
  For 
  the 
  sake 
  of 
  clearness 
  this 
  lining 
  of 
  collared 
  cells 
  is 
  coloured 
  

   red 
  in 
  all 
  the 
  figures. 
  When 
  looked 
  at 
  from 
  above 
  or 
  below 
  this 
  epithelium 
  presents 
  

   the 
  appearance 
  shown 
  in 
  the 
  red-coloured 
  portion 
  of 
  Figure 
  5, 
  PI. 
  VI. 
  It 
  consists 
  of 
  a 
  

   number 
  of 
  retracted 
  collared 
  cells 
  lying 
  side 
  by 
  side. 
  The 
  individual 
  cells 
  are 
  small, 
  in 
  

   Leiicosolenia 
  cavata, 
  for 
  example, 
  measuring 
  about 
  0"0085mni. 
  in 
  diameter. 
  They 
  

   usually 
  appear 
  more 
  or 
  less 
  polygonal 
  from 
  mutual 
  pressure, 
  although 
  at 
  the 
  same 
  

   time, 
  owing, 
  doubtless, 
  to 
  shrinking 
  caused 
  by 
  the 
  action 
  of 
  reagents, 
  they 
  generally 
  

   stand 
  a 
  little 
  apart 
  from 
  one 
  another 
  in 
  the 
  sections, 
  so 
  that 
  the 
  outline 
  of 
  each 
  is 
  distinctly 
  

   visible. 
  The 
  nucleus 
  of 
  each 
  cell 
  is 
  generally 
  clearly 
  visible 
  ; 
  in 
  Leiicosolenia 
  cavata 
  

   its 
  diameter 
  is 
  only 
  about 
  half 
  that 
  of 
  the 
  cell 
  itself. 
  The 
  collared 
  cells, 
  and 
  

   especially 
  the 
  nucleus, 
  stain 
  deeply 
  with 
  the 
  ordmary 
  staining 
  fluids, 
  such 
  as 
  Borax 
  

   Carmine 
  and 
  Kleinenberg's 
  Haematoxylin, 
  and 
  are 
  thus 
  rendered 
  very 
  conspicuous 
  in 
  

   stained 
  preparations. 
  The 
  usual 
  appearance 
  of 
  the 
  collared 
  cells, 
  when 
  seen 
  in 
  sections 
  

   taken 
  at 
  right 
  angles 
  to 
  the 
  surface 
  which 
  they 
  cover, 
  is 
  shown 
  in 
  Figure 
  4, 
  PI. 
  YI. 
  

  

  * 
  " 
  Studies 
  on 
  the 
  Comparative 
  Anatomy 
  ot 
  Sponges, 
  IV.— 
  On 
  the 
  Flagellated 
  Chambers 
  and 
  Ova 
  of 
  Halichondria 
  

   panicea." 
  Quarterly 
  Journal 
  of 
  Microscopical 
  Science, 
  January, 
  1891. 
  

   t 
  Article 
  " 
  Sponges." 
  Encyclopaedia 
  Britannica, 
  Ed. 
  IX. 
  

  

  