﻿A 
  MONOGRAPH 
  OF 
  THE 
  VICTORIAN 
  SPONGES. 
  47 
  

  

  spongorhiza 
  which 
  spreads 
  horizontally 
  in 
  every 
  direction 
  over 
  the 
  substratum 
  on 
  

   which 
  the 
  colony 
  is 
  growing. 
  Occasionally, 
  but 
  only 
  rarely, 
  the 
  Ascon-persons 
  

   anastomose 
  with 
  one 
  another. 
  The 
  spongorhiza 
  also 
  produces 
  short 
  downward 
  

   outgrowths 
  whereby 
  the 
  colony 
  is 
  attached 
  to 
  the 
  substratum. 
  The 
  Ascon-persons 
  

   are 
  cylindrical 
  tubes 
  much 
  wider 
  than 
  the 
  spongorhiza, 
  each 
  provided, 
  when 
  adult, 
  

   with 
  a 
  terminal 
  osculum. 
  They 
  attain 
  a 
  height 
  of 
  about 
  35 
  mm. 
  and 
  a 
  diameter 
  of 
  

   about 
  3*5 
  mm., 
  narrowing 
  slightly 
  towards 
  the 
  osculum. 
  The 
  wall 
  of 
  the 
  tul)e 
  is 
  

   about 
  14 
  mm. 
  thick 
  and 
  distinctly 
  hispid 
  on 
  its 
  outer 
  surface. 
  The 
  colour 
  in 
  spirit 
  

   is 
  white. 
  

  

  Particulars 
  of 
  the 
  canal 
  system 
  are 
  given 
  on 
  pp. 
  25, 
  26. 
  

  

  (/;.) 
  Arrangement 
  of 
  the 
  Skeleton. 
  — 
  The 
  skeleton 
  consists 
  of 
  quadriradiate 
  and 
  

   oxeote 
  spicules. 
  The 
  quadriradiates 
  are 
  very 
  closely 
  packed 
  in 
  the 
  mesoderm, 
  

   forming 
  a 
  rather 
  confused 
  layer, 
  with 
  their 
  facial 
  rays 
  freely 
  overlapping 
  and 
  their 
  

   apical 
  rays 
  projecting 
  into 
  the 
  gastral 
  cavity. 
  The 
  oxeotes 
  have 
  their 
  broader 
  ends 
  

   embedded 
  in 
  the 
  mesoderm 
  and 
  their 
  narrow 
  ends 
  projecting 
  outwards 
  and 
  obli(|uely 
  

   upwards 
  through 
  the 
  ectoderm 
  and 
  giving 
  to 
  the 
  surface 
  of 
  the 
  tube 
  its 
  hispid 
  

   character 
  . 
  

  

  (c.) 
  The 
  spicules 
  (PI. 
  IX., 
  Fig. 
  2). 
  

  

  (1.) 
  Quadriradiates. 
  — 
  These 
  vary 
  a 
  good 
  deal 
  both 
  in 
  size 
  and 
  form. 
  They 
  

   are 
  generally 
  more 
  or 
  less 
  markedly 
  sagittal 
  but 
  not 
  very 
  strongly 
  so, 
  

   and 
  may 
  be 
  almost 
  or 
  quite 
  regular. 
  The 
  rays 
  may 
  be 
  all 
  straight 
  

   or 
  the 
  oral 
  rays 
  may 
  be 
  slightly 
  curved. 
  The 
  apical 
  ray 
  is 
  usually 
  

   short, 
  slender, 
  sharp-pointed, 
  and 
  curved 
  towards 
  the 
  oral 
  angle 
  ; 
  

   much 
  shorter 
  and 
  slenderer 
  than 
  the 
  facial 
  rays 
  ; 
  in 
  a 
  small, 
  but 
  by 
  

   no 
  means 
  insignificant 
  proportion 
  of 
  the 
  spicules, 
  however, 
  it 
  becomes 
  

   enormously 
  exaggerated, 
  measuring 
  as 
  much 
  as 
  0-6 
  mm. 
  in 
  length 
  

   and 
  0-035 
  mm. 
  in 
  diameter 
  at 
  the 
  base, 
  so 
  that 
  its 
  dimensions 
  greatly 
  

   exceed 
  those 
  of 
  the 
  facial 
  rays 
  ; 
  when 
  developed 
  in 
  tliis 
  way 
  it 
  is 
  

   often 
  irregularly 
  bent. 
  The 
  facial 
  rays 
  are 
  usually 
  conical, 
  gradually 
  

   shar})-pointed, 
  and 
  measure 
  about 
  0-2 
  by 
  0'015 
  nun.; 
  sometimes 
  they 
  

   are 
  slightly 
  constricted 
  at 
  the 
  base. 
  

  

  (2.) 
  Oxcotcs. 
  — 
  These 
  are 
  large, 
  asymmetrically 
  fusiform 
  spicules, 
  the 
  widest 
  

   part 
  being 
  much 
  nearer 
  to 
  one 
  end 
  than 
  to 
  the 
  other. 
  They 
  may 
  bo 
  

   quite 
  straight 
  but 
  are 
  more 
  generally 
  somewhat 
  curved 
  like 
  a 
  sickle, 
  

   the 
  curvature 
  may 
  be 
  even 
  or 
  more 
  or 
  less 
  irregular. 
  Tbcy 
  iuc 
  sharply 
  

   pointed 
  at 
  each 
  end. 
  When 
  fully 
  developed 
  they 
  nuMisurc 
  abc)iit 
  01 
  by 
  

   003 
  mm. 
  

  

  