﻿20 
  A 
  MONOGRAPH 
  OF 
  THE 
  VICTORIAN 
  SPONGES. 
  

  

  suppose 
  them 
  to 
  be 
  of 
  vegetable 
  nature. 
  The 
  iodiue-sulphuric 
  acid 
  test 
  is 
  to 
  my 
  

   mind 
  by 
  no 
  means 
  a 
  conclusive 
  one, 
  and 
  in 
  spite 
  of 
  my 
  failure 
  to 
  detect 
  starch 
  or 
  

   cellulose 
  by 
  its 
  means 
  I 
  am 
  inclined 
  to 
  favour 
  the 
  view 
  that 
  these 
  very 
  characteristic 
  

   and 
  remarkable 
  bodies 
  are 
  symbiotic 
  algae. 
  

  

  To 
  judge 
  from 
  a 
  passage 
  in 
  Mr. 
  Carter's 
  description 
  of 
  Leiicosolenia 
  {Clathrina) 
  

   cavata* 
  and 
  from 
  the 
  fact 
  that 
  the 
  yellow 
  granules 
  occur 
  abundantly 
  in 
  a 
  

   specimen 
  of 
  that 
  sponge 
  sent 
  by 
  him 
  to 
  the 
  British 
  Museum 
  and 
  thence 
  to 
  

   me, 
  I 
  think 
  that 
  Mr. 
  Carter 
  must 
  have 
  seen 
  them. 
  The 
  passage 
  referred 
  to 
  

   runs 
  as 
  follows: 
  — 
  " 
  Structure 
  that'al)Ove 
  mentioned, 
  whose 
  staple 
  is 
  the 
  'tubulated 
  

   thread,' 
  of 
  which 
  the 
  wall 
  is 
  very 
  thin 
  and 
  skeletally 
  composed 
  of 
  a 
  single 
  

   layer 
  of 
  radiate 
  spicules 
  held 
  together 
  by 
  sarcode 
  supporting 
  the 
  softer 
  parts, 
  

   which 
  here 
  appear 
  to 
  consist 
  chiefly 
  of 
  a 
  layer 
  of 
  spongozoa 
  in 
  juxtaposition, 
  

   and 
  not 
  gathered 
  into 
  the 
  form 
  of 
  ampullaceous 
  sacs, 
  together 
  ivith 
  a 
  remarkable 
  

   quantity 
  of 
  those 
  organs 
  which 
  consist 
  of 
  nucleated 
  cells 
  surrounded 
  by 
  an 
  abundance 
  

   of 
  glistening 
  spherical 
  granules, 
  which 
  Hceckel 
  has 
  figured 
  and 
  named 
  'nuclei^ 
  

   (Kerne) 
  of 
  his 
  ' 
  Syncytium.'" 
  The 
  portion 
  of 
  the 
  passage 
  italicised 
  leaves 
  no 
  doubt 
  

   in 
  my 
  mind 
  that 
  Mr, 
  Carter 
  refers 
  to 
  the 
  yellow 
  granules, 
  but 
  he 
  is 
  probably 
  mistaken 
  

   in 
  supposing 
  that 
  they 
  have 
  anything 
  to 
  do 
  with 
  the 
  nuclei 
  of 
  Hteckel's 
  " 
  Syncytium." 
  

   The 
  latter 
  are 
  simply 
  the 
  nuclei 
  of 
  the 
  various 
  cells 
  which 
  compose 
  the 
  ectoderm 
  

   and 
  mesoderm, 
  and 
  these 
  also 
  are 
  clearly 
  visible 
  in 
  my 
  preparations 
  of 
  Leucosolenia 
  

   cavata 
  (PI. 
  VI., 
  Fig. 
  5). 
  

  

  The 
  Skeleton. 
  — 
  Having 
  now 
  discussed 
  all 
  the 
  cell-elements 
  which 
  occur 
  embedded 
  

   in 
  the 
  ground-substance 
  of 
  the 
  mesoderm, 
  we 
  come 
  next 
  to 
  the 
  skeleton. 
  

  

  The 
  skeleton 
  of 
  all 
  calcareous 
  sponges 
  consists 
  of 
  isolated 
  spicules 
  never 
  united 
  

   together 
  into 
  fibres 
  or 
  networks 
  as 
  in 
  the 
  sihceous 
  forms. 
  We 
  will 
  first 
  speak 
  of 
  the 
  

   spicules 
  themselves 
  and 
  then 
  of 
  their 
  ari-angement. 
  

  

  The 
  excellent 
  researches 
  of 
  von 
  Ebnerf'have 
  recently 
  thrown 
  much 
  liglit 
  upon 
  the 
  

   physical 
  nature 
  of 
  the 
  calcareous 
  sponge-spicule. 
  According 
  to 
  this 
  author 
  the 
  

   spicule 
  contains 
  no 
  organic 
  basis, 
  but 
  is 
  a 
  crystalline 
  formation, 
  composed 
  chiefly 
  of 
  

   calcspar, 
  but 
  with 
  an 
  admixture 
  of 
  other 
  salts 
  : 
  — 
  "Die 
  Nadeln 
  der 
  Kalkschwamme 
  

   sind 
  hauptsachlich 
  aus 
  Kalkspath 
  bestehende, 
  keine 
  organische 
  Substanz 
  enthaltende 
  

   Individuen 
  von 
  Mischkrystallen, 
  deren 
  aussere 
  Form 
  — 
  ohne 
  Begrenzung 
  durcli 
  wahre 
  

   Krystallflachen 
  — 
  von 
  der 
  specifischen 
  Thatigkeit 
  eines 
  lebenden 
  Organismus 
  bedingt 
  

   ist 
  und 
  deren 
  innere 
  Structur, 
  obwohl 
  vollstandig 
  krystallinisch, 
  durch 
  eine 
  

  

  * 
  " 
  Annals 
  and 
  Magazine 
  of 
  Natural 
  History," 
  June, 
  188G, 
  p. 
  502. 
  

  

  t 
  " 
  L'l)er 
  den 
  feineren 
  Bau 
  der 
  Skelettheile 
  der 
  Kalkschwamme 
  nebst 
  Bemerkungen 
  iiber 
  Kalkskelete 
  iiberhaupt." 
  

   (" 
  Aus 
  dem 
  XCV. 
  Bande 
  der 
  Sitzb. 
  der 
  kais. 
  Akad. 
  der 
  Wissenscli. 
  I. 
  Abth. 
  Marz-Heft., 
  Jahrg. 
  1887.") 
  

  

  