﻿SPONGIIDA. 
  441 
  

  

  in 
  the 
  slenderness 
  of 
  the 
  bihamate 
  spicules, 
  and 
  the 
  almost 
  absolute 
  

   absence 
  of 
  a 
  head 
  to 
  the 
  very 
  slender 
  linear 
  spicule 
  ; 
  the 
  resemblance 
  

   in 
  spiculation 
  seems 
  conclusive 
  as 
  to 
  the 
  generic 
  identity 
  of 
  the 
  

   three 
  forms, 
  in 
  spite 
  of 
  the 
  remarkable 
  differences 
  in 
  the 
  skeleton. 
  

   The 
  mulberry-like 
  bodies 
  described 
  by 
  Marshall 
  in 
  P. 
  solida 
  I 
  can- 
  

   not 
  see 
  in 
  the 
  present 
  species; 
  when 
  treated 
  with 
  hydrochloric 
  acid 
  

   the 
  superficial 
  layer 
  of 
  the 
  dermis 
  parts 
  with 
  all 
  hard 
  elements 
  

   except 
  the 
  spicules 
  and 
  some 
  amorphous 
  transparent 
  fragments. 
  

   Marshall 
  himself 
  does 
  not 
  mention 
  these 
  bodies 
  in 
  P. 
  reticulum, 
  so 
  

   that 
  they 
  cannot 
  be 
  of 
  more 
  than 
  specific 
  or 
  individual 
  importance. 
  

  

  The 
  spiculation 
  of 
  Phoriospongia 
  is 
  perhaps 
  nearer 
  to 
  that 
  of 
  

   Amjjhihctus 
  than 
  of 
  any 
  other 
  genus. 
  Thus, 
  besides 
  Clathria 
  (see 
  

   C. 
  tnherosa, 
  p. 
  444), 
  we 
  have 
  a 
  second 
  genus 
  of 
  Siliceous 
  Sponges 
  

   which 
  may 
  normally 
  exhibit 
  the 
  phenomenon 
  of 
  intussusception 
  

   of 
  sand 
  into 
  the 
  fibre. 
  It 
  seems 
  to 
  me 
  that 
  intussusception 
  is 
  the 
  

   most 
  probable 
  hypothesis 
  on 
  which 
  to 
  account 
  for 
  the 
  presence 
  of 
  

   the 
  sand 
  in 
  this 
  genus, 
  althougli 
  Marshall, 
  whom 
  I 
  understand 
  to 
  

   describe 
  Phonospom/ia 
  as 
  penetrating 
  and 
  spinning 
  up 
  masses 
  of 
  

   sand 
  (" 
  durchziehen 
  und 
  umspinnen 
  Sandraassen, 
  sic 
  zu 
  Klumpen 
  

   vereinigend 
  "), 
  may 
  be 
  right 
  in 
  this 
  inteqjretation 
  of 
  the 
  origin 
  of 
  

   the 
  sand 
  in 
  the 
  genus 
  Phoriospou[/ia 
  ; 
  however, 
  in 
  P. 
  fibrosa 
  we 
  

   find 
  a 
  real 
  system 
  of 
  fibres 
  which 
  does 
  not 
  appear 
  to 
  occur 
  in 
  P. 
  solida 
  

   and 
  reticulum 
  ; 
  and 
  although 
  I 
  have 
  not 
  been 
  able 
  to 
  detect 
  a 
  horny 
  

   material, 
  like 
  that 
  of 
  Di/sidea, 
  uniting 
  the 
  sand 
  grains, 
  which 
  might, 
  

   as 
  held 
  by 
  Bowerbank 
  and 
  Marshall, 
  pick 
  them 
  up, 
  it 
  seems 
  to 
  me 
  

   that, 
  remembering 
  the 
  readiness 
  with 
  which 
  Siliceous 
  Sponges, 
  

   whether 
  possessing 
  a 
  homy 
  fibre 
  or 
  not, 
  take 
  up 
  foreign 
  bodies, 
  

   there 
  is 
  no 
  reason 
  why 
  the 
  sand 
  of 
  PJioriosponr/ia 
  should 
  not 
  be 
  

   taken 
  up, 
  and 
  not 
  be 
  due 
  to 
  the 
  penetration 
  of 
  masses 
  of 
  sand 
  by 
  

   the 
  sponge. 
  This 
  view 
  is 
  supported 
  by 
  the 
  spiculation, 
  which 
  is 
  

   not 
  Suberitid 
  like 
  that 
  of 
  Vioa, 
  but, 
  as 
  above 
  remarked, 
  Desmaci- 
  

   dinc 
  ; 
  the 
  presence 
  of 
  the 
  spinulate 
  spicule 
  is 
  common 
  to 
  it 
  and 
  

   many 
  Desmacidines 
  ; 
  while 
  the 
  absence 
  of 
  the 
  remarkable 
  eversible 
  

   funnel 
  which 
  distinguishes 
  the 
  termination 
  of 
  the 
  excretory 
  canal- 
  

   system 
  in 
  Vioa 
  seems 
  to 
  indicate 
  a 
  different 
  affinity. 
  Reniera 
  fihu- 
  

   lata, 
  Schmidt, 
  to 
  which 
  Marshall 
  refers 
  in 
  support 
  of 
  his 
  view 
  that 
  

   bihamates 
  occur 
  in 
  sponges 
  other 
  than 
  Desmacidinidoe, 
  has 
  been 
  

   placed 
  by 
  Yosmaer 
  in 
  that 
  group 
  under 
  the 
  genus 
  Desmacodes, 
  

   Schmidt, 
  apparent!}' 
  not 
  without 
  reason 
  ; 
  and 
  Schmidt 
  (Spong. 
  Atl. 
  

   Geb. 
  p. 
  40) 
  himself 
  inclines 
  to 
  the 
  view 
  of 
  its 
  Desmacidine 
  affinities 
  ; 
  

   but 
  the 
  presence 
  of 
  bihamates 
  in 
  Suberitidse 
  is 
  hitherto 
  unknown. 
  

  

  ECTYONID.^. 
  

  

  Ectyonida, 
  Carter, 
  Ann. 
  ^ 
  Mag. 
  N. 
  H. 
  1875, 
  xvi. 
  p. 
  133. 
  

  

  Schmidt 
  (Spong. 
  Atl. 
  Geb. 
  1870, 
  p. 
  133) 
  grouped 
  Chaliuopsia 
  

   (^=Ectijon) 
  and 
  its 
  allies, 
  with 
  A.vinella, 
  Phacdlia, 
  &c., 
  under 
  the 
  

   heading 
  Chalinopsidintc 
  ( 
  = 
  Echinonemata, 
  Carter, 
  I. 
  c). 
  Mr. 
  Carter 
  

  

  