﻿74 
  A 
  MONOGRAPH 
  OF 
  THE 
  VICTORIAN 
  SPONGES, 
  

  

  Figure 
  4. 
  — 
  Leucosolenia 
  ventricosa. 
  Vertical 
  section, 
  passing 
  through 
  the 
  

   pseudoscuhun, 
  of 
  the 
  small 
  specimen 
  represented 
  in 
  Figure 
  8, 
  Plate 
  I.; 
  showing 
  the 
  

   arrangement 
  of 
  the 
  canal 
  system. 
  The 
  endoderm 
  is 
  coloured 
  red. 
  (Zeiss 
  aa, 
  Oc. 
  2, 
  

   Camera.) 
  

  

  0. 
  Opening 
  of 
  Ascon-tuhe 
  into 
  pseudogaster 
  (=::osculum 
  in 
  

  

  Figures 
  2 
  and 
  3). 
  

   pd\ 
  The 
  portion 
  of 
  the 
  pseudoderm 
  which 
  forms 
  the 
  lining 
  

   membrane 
  of 
  the 
  pseudogaster. 
  

  

  p.g. 
  Pseudogaster. 
  

  

  p.o. 
  Pseudosculum. 
  

  

  Other 
  lettering 
  as 
  in 
  Figure 
  2. 
  

  

  PLATE 
  V. 
  

  

  Figure 
  1. 
  — 
  Leucosolenia 
  cnvata. 
  A 
  small 
  colony 
  cut 
  in 
  half 
  vertically 
  to 
  show 
  

   the 
  arrangement 
  of 
  the 
  canal 
  system. 
  Enlarged 
  and 
  slightly 
  diagrammatic. 
  In 
  the 
  

   lower 
  portion 
  of 
  the 
  figure 
  are 
  seen 
  the 
  narrow 
  Ascon-tubes 
  separated 
  by 
  wide 
  inter- 
  

   spaces 
  : 
  in 
  the 
  upper 
  portion 
  are 
  seen 
  the 
  narrow, 
  tubular, 
  inhalant 
  canals 
  (=iiiter- 
  

   spaces 
  of 
  the 
  lower 
  portion) 
  separated 
  by 
  wide, 
  irregular 
  cavities 
  (=; 
  merged 
  gastral 
  

   cavities 
  of 
  the 
  Ascon-tubes) 
  out 
  of 
  which 
  the 
  oscula 
  open. 
  

  

  a.t. 
  Ascon-tubes 
  in 
  their 
  primitive 
  condition, 
  forming 
  the 
  lower- 
  

   most 
  portion 
  of 
  the 
  colony. 
  

  

  a'.t'. 
  Gastral 
  cavities 
  of 
  the 
  Ascon-tubes 
  merged 
  into 
  irregular 
  

   spaces. 
  

  

  int. 
  Interspaces 
  between 
  Ascon-tubes. 
  

  

  inf. 
  Interspaces 
  transformed 
  into 
  narrow 
  inhalant 
  canals. 
  

  

  0. 
  Osculum. 
  

  

  p. 
  Pseudopore 
  leading 
  into 
  wide 
  irregular 
  interspace. 
  

  

  p[ 
  Pseudopore 
  leading 
  into 
  narrow, 
  tubular 
  interspace. 
  

  

  pd. 
  Pseudoderm. 
  

  

  Figure 
  2.--Leiicosolenia 
  cnvata. 
  Simplified 
  diagram, 
  based 
  upon 
  Figure 
  1, 
  to 
  

   illustrate 
  the 
  reversal 
  of 
  the 
  canal 
  system. 
  The 
  endoderm 
  is 
  coloured 
  red 
  and 
  the 
  

   space 
  occupied 
  by 
  the 
  merged 
  gastral 
  cavities 
  is 
  coloured 
  black 
  (except 
  where 
  the 
  

   endodermal 
  lining 
  is 
  seen 
  en 
  face). 
  For 
  the 
  sake 
  of 
  clearness 
  all 
  the 
  tubes 
  are 
  

   represented 
  as 
  unbranched 
  and 
  running 
  vertically 
  instead 
  of 
  in 
  every 
  direction 
  as 
  

  

  