﻿NO. 
  1946. 
  PACIFIC 
  MEDUSAE 
  AND 
  SIPHONOPHORAE—BIGELOW. 
  67 
  

  

  Station 
  4800, 
  300-0 
  fatlioms; 
  3 
  colonies 
  with 
  5, 
  5, 
  and 
  6 
  nectophores 
  

   and 
  16 
  loose 
  nectophores. 
  

  

  Station 
  4897, 
  300-0 
  fathoms; 
  6 
  loose 
  nectophores. 
  

  

  Station 
  4928, 
  300-0 
  fathoms; 
  part 
  of 
  a 
  colony 
  with 
  3 
  nectophores. 
  

  

  Station 
  4951, 
  300-0 
  fathoms; 
  part 
  of 
  a 
  colony 
  with 
  3 
  nectophores. 
  

  

  Station 
  5030, 
  300-0 
  fathoms 
  ; 
  3 
  colonies 
  with 
  6, 
  6, 
  and 
  7 
  nectophores 
  

   and 
  14 
  loose 
  nectophores. 
  

  

  As 
  a 
  whole, 
  the 
  material 
  is 
  in 
  good 
  condition, 
  but 
  the 
  stem 
  is 
  

   invariably 
  so 
  strongly 
  contracted 
  that 
  it 
  is 
  difficult 
  to 
  disentangle 
  the 
  

   prolonged 
  '^knospungzone," 
  which 
  bears 
  the 
  nectophores, 
  from 
  it. 
  

  

  These 
  specimens 
  are 
  especially 
  interesting, 
  because 
  comparison 
  

   between 
  them 
  and 
  the 
  eastern 
  Pacific 
  series 
  of 
  V. 
  spinosa 
  shows 
  that 
  

   the 
  difference 
  in 
  the 
  conformation 
  of 
  the 
  nectophores 
  which 
  has 
  been 
  

   used 
  to 
  separate 
  the 
  two 
  specifically 
  (191 
  1&) 
  is 
  visible 
  from 
  a 
  very 
  

   early 
  stage 
  in 
  development. 
  In 
  spinosa 
  the 
  nectophores 
  are 
  spinous 
  

   on 
  the 
  lateral 
  and 
  dorsal 
  facets, 
  as 
  well 
  as 
  on 
  the 
  margins 
  of 
  the 
  facets. 
  

   This 
  type 
  of 
  spinosity 
  is 
  seen 
  in 
  very 
  young 
  nectophores 
  as 
  well 
  as 
  in 
  

   older 
  ones 
  (191 
  1&, 
  pi. 
  15, 
  figs. 
  9-11), 
  but 
  m 
  pentacantha 
  the 
  surfaces 
  

   of 
  the 
  facets 
  are 
  smooth 
  at 
  all 
  ages 
  (pi. 
  5, 
  fig. 
  7). 
  

  

  It 
  appears 
  that 
  there 
  is 
  a 
  good 
  deal 
  of 
  variation 
  in 
  the 
  degree 
  to 
  

   which 
  spines 
  are 
  developed 
  on 
  the 
  ridges 
  limiting 
  the 
  facets. 
  Chun 
  

   (1897&) 
  shows 
  numerous 
  pointed 
  spines 
  in 
  these 
  regions, 
  and 
  the 
  

   Biscayan 
  specimen 
  recorded 
  by 
  me 
  was 
  likewise 
  slightly 
  spmous 
  on 
  

   the 
  margin 
  of 
  the 
  facets. 
  But 
  in 
  the 
  present 
  series 
  the 
  older 
  necto- 
  

   phores 
  have 
  no 
  spines 
  at 
  all. 
  The 
  ridges, 
  like 
  the 
  facets, 
  are 
  perfectly 
  

   smooth 
  (pi. 
  5, 
  fig. 
  7), 
  though 
  in 
  very 
  youngest 
  nectophores 
  the 
  

   margins 
  of 
  the 
  facets 
  are 
  always 
  (?) 
  more 
  or 
  less 
  irregular 
  (pi. 
  5, 
  

   fig. 
  8), 
  and 
  I 
  found 
  one 
  in 
  which 
  they 
  are 
  distinctly 
  spinous. 
  

  

  The 
  nectophores 
  of 
  the 
  two 
  species 
  likewise 
  difi'er 
  in 
  details 
  of 
  form, 
  

   but 
  this 
  is 
  more 
  clearly 
  shown 
  by 
  figures 
  (pi. 
  5, 
  fig. 
  7, 
  19116, 
  pi. 
  15, 
  

   figs. 
  9, 
  10) 
  than 
  verbally. 
  

  

  Another 
  feature 
  which 
  proves 
  to 
  be 
  diagnostic 
  is 
  the 
  ''ventral 
  

   sinus," 
  into 
  which 
  the 
  ventral 
  subumbral 
  canal 
  is 
  expanded. 
  In 
  

   spinosa 
  this 
  cavity 
  covers 
  nearly 
  the 
  whole 
  of 
  the 
  upper 
  surface 
  of 
  the 
  

   subumbrella 
  in 
  very 
  young 
  nectophores, 
  and 
  as 
  growth 
  progresses 
  

   it 
  becomes 
  gradually 
  obliterated, 
  the 
  coalescence 
  progressing 
  from 
  

   the 
  dorsal 
  side 
  and 
  from 
  the 
  margins, 
  in 
  such 
  a 
  way 
  that 
  the 
  sinus 
  is 
  

   finally 
  narrowed 
  to 
  two 
  lateral 
  wings, 
  which 
  are 
  narrowest 
  next 
  the 
  

   canals 
  (191 
  1&, 
  pi. 
  15, 
  figs. 
  9, 
  12) 
  ; 
  and 
  in 
  this 
  form 
  it 
  is 
  to 
  be 
  seen 
  in 
  

   the 
  largest 
  nectophores 
  which 
  I 
  examined. 
  

  

  In 
  the 
  youngest 
  nectophores 
  of 
  pentacantha 
  the 
  sinus 
  is 
  smaller 
  

   (pi. 
  5, 
  fig. 
  8) 
  than 
  in 
  spinosa 
  at 
  a 
  corresponding 
  stage, 
  and 
  with 
  the 
  

   growth 
  of 
  the 
  bell 
  it 
  becomes 
  narrower 
  and 
  narrower, 
  taking 
  on 
  a 
  

   heart-shaped 
  (pi. 
  5, 
  fig. 
  9) 
  and 
  finally 
  a 
  linear 
  outHne 
  (pi. 
  5, 
  fig. 
  7), 
  

  

  