﻿A 
  MONOGKAPH 
  OF 
  THE 
  VICTORIAN 
  SPONGES. 
  75 
  

  

  they 
  really 
  do 
  {cf. 
  Figure 
  1). 
  The 
  transition 
  between 
  the 
  normal 
  and 
  the 
  reversed 
  

   portions 
  of 
  the 
  canal 
  system 
  takes 
  place 
  in 
  the 
  area 
  marked 
  x, 
  where 
  it 
  will 
  be 
  seen 
  

   that 
  there 
  are 
  really 
  no 
  tubes 
  at 
  all 
  but 
  two 
  systems 
  of 
  spaces 
  separated 
  by 
  an 
  

   undulating 
  membrane. 
  

  

  Lettering 
  as 
  in 
  Figure 
  1. 
  

  

  Figure 
  3. 
  — 
  Leiicosolenia 
  tripodifera. 
  A 
  small 
  specimen 
  the 
  upper 
  portion 
  of 
  

   which 
  has 
  been 
  divided 
  longitudinally 
  so 
  as 
  to 
  exhibit 
  the 
  arrangement 
  of 
  the 
  canal 
  

   system. 
  The 
  red 
  colour 
  indicates 
  the 
  distribution 
  of 
  the 
  collared 
  cells, 
  which 
  are 
  

   visible 
  wherever 
  the 
  central 
  cavity 
  or 
  the 
  radial 
  tubes 
  have 
  been 
  cut 
  into. 
  The 
  

   figure 
  also 
  shows 
  how 
  the 
  radial 
  tubes 
  originate 
  as 
  little 
  hollow 
  diverticula 
  {ft') 
  of 
  

   the 
  wall 
  of 
  the 
  central 
  cavity 
  a 
  short 
  way 
  below 
  the 
  osculum, 
  at 
  first 
  uubranched 
  

   but 
  as 
  they 
  grow 
  older 
  [r.t.) 
  branching 
  freely. 
  

  

  gx. 
  Gastral 
  cavity. 
  

  

  int. 
  Interspaces 
  between 
  radial 
  tubes. 
  

  

  0. 
  Osculum. 
  

  

  op. 
  Openings 
  of 
  radial 
  tubes 
  into 
  gastral 
  cavity. 
  

  

  r.t. 
  Kadial 
  tubes. 
  

  

  v',t'. 
  Young 
  radial 
  tubes. 
  

  

  Figure 
  4. 
  — 
  Leiicosolenia 
  tripodifera. 
  Small 
  portion 
  of 
  a 
  thin 
  section 
  along 
  the 
  

   radial 
  tubes 
  seen 
  under 
  a 
  low 
  power 
  of 
  the 
  microscope. 
  In 
  the 
  upper 
  right-hand 
  

   part 
  of 
  the 
  section 
  the 
  tubes 
  are 
  not 
  cut 
  into 
  and 
  their 
  walls 
  are 
  seen 
  en 
  face. 
  

   Elsewhere 
  the 
  tubes 
  are 
  cut 
  right 
  through 
  so 
  as 
  to 
  show 
  their 
  walls 
  only 
  in 
  section. 
  

   The 
  endoderm 
  is 
  coloured 
  red 
  and 
  the 
  spicules 
  blue. 
  

  

  a. 
  Anastomosis 
  between 
  two 
  neighbouring 
  radial 
  tubes. 
  

  

  pr. 
  Prosopyle. 
  

  

  t.s. 
  Large 
  "tripod" 
  spicules 
  protecting 
  the 
  blind 
  outer 
  ends 
  of 
  

   the 
  radial 
  tubes. 
  

  

  Other 
  lettering 
  as 
  in 
  Figure 
  o. 
  

  

  PLATE 
  VI. 
  

  

  Figure 
  I. 
  — 
  Leiicosolenia 
  stolonifer. 
  Small 
  portion 
  of 
  a 
  transverse 
  section 
  of 
  the 
  

   wall 
  of 
  an 
  Ascon-pcrson. 
  The 
  endoderm 
  is 
  coloured 
  red 
  and 
  tlu^ 
  spicules 
  blue. 
  

   (Zeiss 
  0, 
  Oc. 
  2.) 
  

  

  