﻿A 
  MONOGRAPH 
  OF 
  THE 
  VICTORIAN 
  SPONaES. 
  35 
  

  

  In 
  many 
  of 
  the 
  older 
  tubes 
  developing 
  embryos* 
  were 
  found 
  suspended 
  in 
  

   the 
  middle 
  of 
  the 
  gastral 
  cavity, 
  embedded 
  in 
  the 
  mesoderm 
  and 
  surrounded 
  by 
  a 
  

   peculiar 
  capsule 
  ; 
  but 
  these 
  have 
  already 
  been 
  described. 
  

  

  A 
  similar, 
  if 
  not 
  identical, 
  condition 
  of 
  the 
  Ascon-tubes, 
  characterised 
  by 
  the 
  

   formation 
  of 
  endogastric 
  septa, 
  was 
  long 
  since 
  described 
  by 
  Hfeckel 
  in 
  his 
  Ascetta 
  

   primordialis 
  var. 
  loculosn 
  and 
  A. 
  clathrus 
  var. 
  clathriiin.\ 
  

  

  Section 
  III. 
  rabiata. 
  

  

  This 
  section 
  of 
  the 
  genus, 
  as 
  its 
  name 
  implies, 
  includes 
  such 
  species 
  as 
  exhibit 
  a 
  

   radiate 
  structure 
  — 
  the 
  sponge 
  consisting 
  of 
  a 
  single 
  central 
  Ascon-tube 
  from 
  which 
  

   smaller 
  tubes 
  are 
  budded 
  off 
  radially. 
  

  

  The 
  only 
  example 
  of 
  the 
  section 
  with 
  which 
  I 
  am 
  as 
  yet 
  acquainted 
  is 
  

   Leucosolenia 
  iripodifera, 
  a 
  very 
  interesting 
  sponge 
  originally 
  described 
  by 
  Mr. 
  

   Carter 
  under 
  the 
  name 
  Clathrina 
  tripodifern. 
  Fortunately, 
  a 
  considerable 
  number 
  

   of 
  specimens 
  of 
  this 
  sponge 
  have 
  come 
  into 
  my 
  hands, 
  including 
  a 
  piece 
  of 
  one 
  of 
  Mr. 
  

   Carter's 
  type 
  specimens 
  in 
  the 
  British 
  Museum, 
  so 
  that 
  I 
  have 
  been 
  able 
  fully 
  to 
  

   elucidate 
  the 
  anatomy 
  of 
  the 
  species, 
  an 
  undertaking 
  greatly 
  facilitated 
  by 
  the 
  

   large 
  size 
  to 
  which 
  the 
  sponge 
  grows. 
  One 
  specimen 
  in 
  my 
  possession 
  is 
  nearly 
  

   four 
  inches 
  (100 
  mm.) 
  in 
  height, 
  and 
  two 
  inches 
  (50 
  mm.) 
  in 
  diameter, 
  it 
  is 
  

   represented 
  of 
  the 
  natural 
  size 
  in 
  Figure 
  G, 
  Plate 
  II. 
  The 
  remainder 
  of 
  my 
  

   specimens, 
  however, 
  are 
  none 
  of 
  them 
  more 
  than 
  about 
  one 
  inch 
  and 
  a 
  half 
  (38 
  mm.) 
  

   high, 
  and 
  three 
  quarters 
  of 
  an 
  inch 
  (19 
  mm.) 
  in 
  diameter 
  (PI. 
  II., 
  Fig. 
  5). 
  

  

  The 
  whole 
  sponge 
  resembles 
  a 
  very 
  thick 
  walled 
  sack. 
  The 
  cavity 
  of 
  the 
  sack 
  is 
  

   the 
  gastral 
  cavity 
  of 
  the 
  central 
  Ascon-tube, 
  which 
  is 
  extraordinarily 
  large, 
  its 
  

   transverse 
  diameter 
  being 
  as 
  great 
  as, 
  or 
  greater 
  than, 
  the 
  thickness 
  of 
  the 
  wall 
  of 
  the 
  

   sack. 
  This 
  cavity 
  terminates 
  in 
  a 
  wide 
  osculumat 
  the 
  summit 
  of 
  the 
  sponge 
  (PI. 
  V,, 
  

   Fig. 
  3). 
  The 
  thick 
  wall 
  of 
  the 
  sack 
  is 
  made 
  up 
  of 
  a 
  great 
  number 
  of 
  radial 
  

   tubes 
  given 
  off 
  fiom 
  the 
  central 
  tube, 
  into 
  which 
  they 
  open 
  by 
  means 
  of 
  

   irregular 
  groups 
  of 
  openings 
  (PI. 
  V., 
  Fig. 
  3). 
  The 
  way 
  in 
  which 
  these 
  radial 
  

   tubes 
  are 
  formed 
  is 
  very 
  plainly 
  shown 
  in 
  one 
  of 
  my 
  specimens, 
  represented 
  in 
  

   a 
  slightly 
  diagrammatic 
  manner 
  in 
  Figure 
  3, 
  Plate 
  V. 
  At 
  the 
  summit 
  of 
  the 
  sponge, 
  

   immediately 
  below 
  the 
  osculum, 
  the 
  wall 
  of 
  the 
  largo 
  central 
  Ascon-tube 
  is 
  very 
  

   thin 
  and 
  membranous 
  and 
  there 
  are 
  no 
  radial 
  tubes 
  tleveloped 
  as 
  yei, 
  so 
  that 
  it 
  looks 
  

   as 
  if 
  the 
  osculum 
  were 
  surrounded 
  by 
  a 
  membranous 
  oscular 
  fringe. 
  The 
  

  

  * 
  In 
  the 
  closely-allied 
  siiecios 
  J.furo^olcnia 
  (h'piwami, 
  ova 
  only 
  were 
  foitiiil, 
  in 
  tlie 
  Hiinip 
  jiosltion 
  as 
  tlio 
  embryos 
  

   in 
  I,, 
  ivihoiii. 
  

  

  I 
  " 
  Dio 
  Kalkscliwiiiunie," 
  Vol. 
  2, 
  pp. 
  UH, 
  :15. 
  Vol. 
  a, 
  I'l. 
  IV., 
  Kig. 
  5. 
  

  

  