﻿104 
  Messrs. 
  H. 
  J. 
  Carter 
  and 
  R. 
  Hope 
  on 
  a 
  neio 
  

  

  merits 
  of 
  the 
  two 
  sponges, 
  that 
  : 
  — 
  1, 
  while 
  the 
  main 
  skeleton- 
  

   spicula 
  of 
  the 
  former 
  are 
  in 
  length 
  intermediate 
  between 
  the 
  

   two 
  chief 
  divisions 
  of 
  those 
  of 
  M. 
  armata, 
  they 
  are 
  little 
  more 
  

   than 
  one 
  third 
  as 
  thick 
  ; 
  2, 
  the 
  characteristic 
  spined 
  styles 
  

   of 
  M. 
  armata 
  are 
  entirely 
  absent 
  from 
  the 
  sponge 
  under 
  con- 
  

   sideration, 
  being 
  replaced 
  by 
  spicules 
  approaching 
  more 
  

   nearly 
  to 
  the 
  corresponding 
  form 
  in 
  M. 
  atrosanguinea. 
  

   Turning 
  to 
  the 
  microsclera, 
  we 
  find, 
  1, 
  that 
  while 
  none 
  of 
  the 
  

   other 
  spicules 
  of 
  our 
  sponge 
  attain 
  to 
  the 
  dimensions 
  of 
  those 
  

   of 
  M. 
  armata, 
  the 
  toxa 
  exceed 
  in 
  length 
  those 
  of 
  the 
  latter 
  

   sponge 
  by 
  fully 
  one 
  half, 
  viz. 
  "29 
  against 
  '19 
  millim., 
  the 
  

   largest 
  respectively 
  ; 
  if 
  the 
  average 
  be 
  taken, 
  the 
  proportional 
  

   difference 
  will 
  be 
  found 
  fully 
  as 
  great. 
  They 
  differ 
  also 
  in 
  

   possessing 
  in 
  the 
  one 
  case 
  spined 
  and 
  in 
  the 
  other 
  perfectly 
  

   smooth 
  tips. 
  2. 
  On 
  the 
  other 
  hand 
  the 
  chelae 
  of 
  this 
  sponge 
  

   are 
  on 
  the 
  average 
  only 
  about 
  two 
  thirds 
  as 
  long 
  as 
  those 
  of 
  

   M. 
  armata 
  and 
  much 
  less 
  numerous. 
  

  

  The 
  possession 
  of 
  this 
  specimen 
  of 
  M. 
  armata 
  enabled 
  me 
  

   to 
  bring 
  to 
  the 
  notice 
  of 
  Mr. 
  Carter 
  the 
  differences 
  between 
  

   the 
  two 
  sponges, 
  and 
  these 
  proved, 
  as 
  above 
  stated, 
  to 
  be 
  in 
  

   his 
  judgment 
  of 
  specific 
  value. 
  The 
  points 
  more 
  especially 
  

   relied 
  upon 
  in 
  support 
  of 
  this 
  view 
  Mr. 
  Carter 
  leaves 
  me 
  to 
  

   state. 
  They 
  are 
  as 
  follows: 
  — 
  1, 
  the 
  difference 
  in 
  the 
  

   skeletal 
  arrangement 
  of 
  the' 
  two 
  forms, 
  which 
  is 
  exceedingly 
  

   striking 
  on 
  an 
  inspection 
  of 
  balsam 
  preparations, 
  the 
  " 
  scopu- 
  

   liform 
  bundles 
  " 
  of 
  M. 
  spinarcus 
  (fig. 
  A, 
  1) 
  being 
  weak 
  and 
  

   " 
  unarmed," 
  while 
  those 
  of 
  the 
  aptly-named 
  M. 
  armata 
  

   angrily 
  bristle 
  on 
  all 
  sides 
  with 
  their 
  thorny 
  styles, 
  and 
  recall 
  

   vividly 
  the 
  trophies 
  of 
  swords 
  and 
  bayonets 
  which 
  decorate 
  

   an 
  armoury 
  (fig. 
  B, 
  1) 
  ; 
  2, 
  the 
  complete 
  absence 
  in 
  the 
  former 
  

   sponge 
  of 
  the 
  characteristic 
  spined 
  style 
  of 
  the 
  latter 
  ; 
  and 
  

   3, 
  the 
  spination 
  and 
  great 
  increase 
  in 
  size, 
  both 
  absolutely 
  

   and 
  particularly 
  relatively, 
  of 
  the 
  toxa 
  in 
  M. 
  spinarcus. 
  As 
  

   regards 
  the 
  last 
  point, 
  the 
  largest 
  main 
  skeletal 
  spicules 
  are 
  

   to 
  the 
  largest 
  toxa 
  in 
  length 
  in 
  M. 
  armata 
  as 
  3*3 
  to 
  1, 
  in 
  M. 
  

   spinarcus 
  only 
  as 
  1*66 
  to 
  1. 
  If 
  the 
  average 
  of 
  the 
  spicules 
  

   were 
  taken, 
  the 
  discrepancy 
  would 
  be, 
  I 
  believe, 
  quite 
  as 
  

   great 
  ; 
  but 
  where 
  the 
  spicules 
  vary 
  so 
  very 
  much 
  in 
  size, 
  the 
  

   average 
  must 
  be 
  so 
  much 
  a 
  matter 
  of 
  appreciation 
  that 
  it 
  

   seems 
  better 
  to 
  give 
  measurements 
  of 
  the 
  largest 
  spicules, 
  

   which 
  are 
  easily 
  recognized. 
  

  

  From 
  M. 
  atrosanguinea 
  our 
  sponge 
  differs 
  chiefly 
  in 
  the 
  

   shape 
  and 
  spination 
  of 
  the 
  main 
  skeletal 
  spicules 
  and 
  in 
  the 
  

   form, 
  size, 
  and 
  spination 
  of 
  the 
  toxa. 
  Slighter 
  divergences 
  in 
  

   the 
  other 
  spicula 
  will 
  be 
  best 
  appreciated 
  by 
  inspection 
  of 
  the 
  

   annexed 
  Plate 
  VI. 
  figs. 
  A 
  and 
  C, 
  2-6 
  inclusively. 
  The 
  

  

  