﻿42 
  A 
  MONOGRAPH 
  OF 
  THE 
  VICTORIAN 
  SPONGES. 
  

  

  All 
  forms 
  of 
  Homocoela, 
  no 
  matter 
  what 
  their 
  anatomical 
  peciiHarities, 
  which 
  happen 
  

   to 
  have 
  spicules 
  of 
  the 
  same 
  shape, 
  are 
  brought 
  by 
  Hffickel 
  under 
  a 
  single 
  "species." 
  

   Now 
  there 
  are 
  only 
  three 
  fundamental 
  forms 
  of 
  spicules 
  in 
  the 
  entire 
  group 
  of 
  calcareous 
  

   sponges, 
  viz., 
  the 
  triradiate, 
  quadriradiate 
  and 
  oxeote, 
  and 
  each 
  of 
  these 
  may 
  vary 
  

   greatly 
  in 
  shape 
  within 
  a 
  single 
  specimen. 
  Moreover 
  some 
  portions 
  of 
  a 
  colony 
  may 
  

   contain 
  say 
  oxeote 
  or 
  quadriradiate 
  sj^icules, 
  while 
  other 
  portions 
  taken 
  from 
  the 
  

   same 
  specimen 
  may 
  contain 
  none. 
  Haeckel 
  was 
  well 
  aw^are 
  of 
  this 
  variation 
  in 
  the 
  

   spiculation 
  and 
  hence 
  his 
  " 
  connective 
  varieties," 
  which 
  often 
  bring 
  the 
  same 
  species 
  

   under 
  two 
  or 
  three 
  distinct 
  genera. 
  

  

  I 
  grant 
  that 
  there 
  are 
  certain 
  forms 
  of 
  spicules 
  which 
  may 
  be 
  regarded 
  as 
  typical 
  

   for 
  each 
  species, 
  but 
  the 
  presence 
  of 
  similar 
  spicules 
  is 
  not 
  alone 
  sufficient 
  to 
  justify 
  

   us 
  in 
  including 
  under 
  one 
  speciHc 
  name 
  forms 
  which 
  otherwise 
  differ 
  widely 
  in 
  

   organisation. 
  

  

  Hffickel's 
  natural 
  genera 
  are 
  particularly 
  artificial, 
  and 
  this 
  might 
  be 
  expected 
  

   when 
  we 
  see 
  that 
  the 
  same 
  series 
  of 
  generic 
  diagnoses, 
  depending 
  solely 
  upon 
  the 
  

   combinations 
  of 
  the 
  three 
  types 
  of 
  spicules, 
  is 
  made 
  to 
  serve 
  for 
  all 
  his 
  three 
  families 
  

   of 
  calcareous 
  sponges. 
  

  

  Since 
  neither 
  of 
  Hseckel's 
  alternative 
  systems 
  will 
  satisfy 
  the 
  requirements 
  of 
  

   the 
  modern 
  zoologist 
  we 
  must 
  find 
  a 
  new 
  method, 
  and 
  in 
  this 
  new 
  method 
  we 
  must 
  

   be 
  content 
  to 
  follow 
  the 
  example 
  of 
  Avorkers 
  in 
  other 
  branches 
  of 
  zoology 
  and 
  give 
  

   up 
  all 
  hope 
  of 
  finding 
  a 
  royal 
  road 
  to 
  classification. 
  In 
  other 
  words, 
  we 
  must 
  make 
  

   use 
  of 
  as 
  many 
  characters 
  as 
  possible 
  and 
  not 
  of 
  as 
  few, 
  and 
  in 
  this 
  way 
  — 
  classifying 
  

   by 
  an 
  assemblage 
  of 
  characters* 
  — 
  we 
  may 
  fairly 
  hope 
  to 
  make 
  satisfactory 
  progress. 
  

   At 
  the 
  same 
  time 
  we 
  must 
  not 
  forget 
  that 
  Hseckel's 
  classification 
  of 
  the 
  Calcarea 
  was 
  

   the 
  first 
  serious 
  attempt 
  at 
  anything 
  of 
  the 
  kind 
  ; 
  that 
  he 
  had 
  an 
  extremely 
  difficult 
  

   task 
  to 
  deal 
  with, 
  and 
  that 
  immense 
  credit 
  is 
  due 
  to 
  him 
  for 
  the 
  energy 
  and 
  

   perseverance 
  with 
  which 
  he 
  led 
  the 
  way 
  in 
  this 
  department 
  of 
  biology. 
  All 
  schemes 
  

   of 
  classification 
  are 
  but 
  tentative 
  and 
  each 
  must 
  give 
  place 
  to 
  later 
  modifications 
  as 
  

   our 
  knowledge 
  advances, 
  for 
  evolution 
  plays 
  as 
  important 
  a 
  part 
  in 
  our 
  study 
  of 
  

   organisms 
  as 
  it 
  does 
  in 
  the 
  history 
  of 
  the 
  organisms 
  themselves. 
  

  

  Of 
  course 
  we 
  shall 
  find 
  that 
  different 
  characters 
  often 
  contradict 
  one 
  another, 
  

   forms 
  Avhich 
  agree 
  in 
  spiculation 
  may 
  differ 
  widely 
  in 
  canal-system, 
  and 
  vice-versa. 
  

   So 
  great 
  is 
  the 
  variation 
  in 
  both 
  these 
  characters 
  amongst 
  the 
  Calcarea 
  Homocoela 
  

   and 
  so 
  difficult 
  is 
  it 
  to 
  determine 
  which 
  is 
  the 
  most 
  important 
  that 
  Polejaeff' 
  has, 
  in 
  

   his 
  work 
  on 
  the 
  Calcarea 
  of 
  the 
  " 
  Challenger 
  " 
  Expedition, 
  abandoned 
  all 
  Haeckel's 
  

   seven 
  natural 
  genera 
  of 
  Homocoela 
  and 
  fallen 
  Imck 
  upon 
  the 
  old 
  genus 
  Leucosolenia 
  

  

  * 
  " 
  No 
  doubt 
  organic 
  beings, 
  like 
  all 
  other 
  objects, 
  can 
  be 
  classed 
  in 
  many 
  ways, 
  either 
  artificially 
  by 
  single 
  

   characters 
  or 
  more 
  naturally 
  by 
  a 
  number 
  of 
  characters."— 
  Darwin, 
  " 
  Origin 
  of 
  Species," 
  Ed. 
  VI., 
  p. 
  364. 
  

  

  