﻿454 
  R. 
  Ruedemann 
  — 
  Mode 
  of 
  Growth 
  and 
  Development 
  

  

  (4) 
  The 
  majority 
  of 
  the 
  fossils 
  present 
  a 
  large 
  subquadratic 
  

   impression 
  which 
  overlaps 
  the 
  gonangia, 
  and 
  sometimes 
  even 
  

   the 
  proximal 
  ends 
  of 
  the 
  stipes. 
  Some 
  specimens 
  of 
  D. 
  jpris- 
  

   tiniformis 
  Hall, 
  found 
  in 
  a 
  limestone-layer 
  which 
  is 
  interpo- 
  

   lated 
  in 
  the 
  shale, 
  reveal 
  the 
  fact 
  that 
  this 
  impression 
  belongs 
  

   to 
  an 
  organ 
  which 
  was 
  made 
  up 
  of 
  a 
  large 
  spherical 
  segment 
  

   on 
  the 
  upper 
  side 
  and 
  a 
  smaller 
  one 
  on 
  the 
  under 
  side 
  of 
  a 
  

   quadrangular 
  plate. 
  The 
  latter 
  has 
  a 
  system 
  of 
  furrows 
  paral- 
  

   lel 
  to 
  the 
  margin. 
  The 
  author 
  compares 
  the 
  whole 
  organ 
  with 
  

   the 
  air-bladder 
  or 
  pneumatocyst 
  of 
  the 
  Discoidece, 
  a 
  family 
  of 
  

   the 
  SvphonophorcB, 
  on 
  account 
  of 
  its 
  size, 
  its 
  being 
  the 
  top- 
  

   most 
  organ, 
  and 
  on 
  account 
  of 
  the 
  apparent 
  absence 
  of 
  any 
  

   structure 
  — 
  besides 
  the 
  furrowing 
  in 
  the 
  plate 
  which 
  reminds 
  

   much 
  of 
  the 
  system 
  of 
  canals 
  in 
  the 
  float 
  of 
  the 
  Discoidece. 
  

  

  We 
  may 
  infer 
  from 
  the 
  preceding 
  observations 
  that 
  the 
  

   colonial 
  stock 
  was 
  carried 
  by 
  a 
  large 
  air-bladder, 
  to 
  the 
  under- 
  

   side 
  of 
  which 
  was 
  attached 
  the 
  funicle. 
  The 
  latter 
  was 
  

   enclosed 
  in 
  the 
  central 
  disc 
  and 
  this 
  was 
  surrounded 
  by 
  a 
  ver- 
  

   ticil 
  of 
  vesicles, 
  the 
  "gonangia, 
  which 
  produced 
  the 
  siculas. 
  

   Below 
  the 
  verticil 
  of 
  gonangia 
  and 
  suspended 
  from 
  the 
  funicle 
  

   was 
  the 
  tuft 
  of 
  stipes. 
  

  

  (5) 
  A 
  close 
  observation 
  of 
  the 
  siculse, 
  which 
  are 
  found 
  so 
  

   numerously 
  on 
  the 
  slabs, 
  detected 
  the 
  fact 
  that 
  the 
  siculse, 
  at 
  

   the 
  time 
  of 
  developing 
  the 
  first 
  two 
  hydrothecse, 
  possessed 
  a 
  

   quadrangular 
  plate, 
  joined 
  by 
  a 
  small 
  node 
  in 
  the 
  center 
  to 
  the 
  

   end 
  of 
  the 
  filiform 
  proximal 
  process. 
  On 
  young 
  stipes 
  with 
  

   seven 
  hydrothecse 
  on 
  one 
  side 
  and 
  six 
  on 
  the 
  other, 
  can 
  be 
  

   already 
  discerned 
  four 
  oval, 
  distinctly 
  furrowed 
  impressions 
  

   around 
  the 
  central 
  node. 
  

  

  The 
  first 
  appearing 
  quadrangular 
  plate 
  — 
  or 
  probably 
  vesicle 
  

   — 
  develops 
  into 
  the 
  pneumatocyst, 
  the 
  central 
  node 
  into 
  the 
  

   funicle 
  and 
  central 
  disc 
  ; 
  and 
  in 
  the 
  small 
  oval 
  impressions 
  we 
  

   most 
  probably 
  see 
  the 
  budding 
  gonangia. 
  The 
  sicula, 
  there- 
  

   fore, 
  which 
  grows 
  out 
  to 
  the 
  primary 
  stipe 
  develops 
  first 
  the 
  

   floating 
  organ 
  and 
  then 
  the 
  central 
  organs. 
  

  

  It 
  deserves 
  to 
  be 
  noted 
  that 
  the 
  new 
  hydrothecaB 
  of 
  the 
  

   primary 
  stipe 
  sprout 
  in 
  the 
  direction 
  towards 
  the 
  central 
  organs 
  

   while 
  the 
  sicula 
  remains 
  in 
  all 
  stages 
  of 
  development 
  at 
  the 
  

   opposite 
  end 
  of 
  the 
  central 
  organs, 
  i. 
  e., 
  at 
  the 
  distal 
  end. 
  

  

  "Whether 
  the 
  primary 
  stipe 
  produces 
  first 
  new 
  siculae, 
  some 
  

   of 
  which 
  remain 
  in 
  connection 
  with 
  the 
  center, 
  forming 
  new 
  

   stipes 
  and 
  by 
  these 
  the 
  compound 
  frond, 
  or 
  whether 
  other 
  

   detached 
  siculse 
  gain 
  connection 
  with 
  the 
  new 
  center 
  of 
  the 
  

   first 
  stipe, 
  could 
  not 
  be 
  decided. 
  The 
  fact, 
  however, 
  is 
  that 
  

   fronds 
  with 
  one 
  full-grown 
  stipe, 
  the 
  primary 
  one, 
  and 
  several 
  

   young 
  ones 
  are 
  a 
  rather 
  common 
  occurrence, 
  further 
  that 
  

   fronds 
  have 
  been 
  found 
  to 
  the 
  center 
  of 
  which 
  siculse 
  without 
  

  

  