﻿NO. 
  1946. 
  PACIFIC 
  MEDUSAE 
  AND 
  SIPHONOPHORAE—BIGELOW. 
  29 
  

  

  side 
  agrees 
  very 
  well 
  with 
  Haeckel's 
  figure 
  (1881, 
  pi. 
  2, 
  fig. 
  1), 
  the 
  

   folds 
  and 
  the 
  corresponding 
  transverse 
  diverticula 
  of 
  the 
  radial 
  

   canals 
  being 
  very 
  regular, 
  about 
  20 
  on 
  each 
  side, 
  and 
  so 
  long 
  that 
  the 
  

   organ 
  as 
  a 
  whole 
  is 
  of 
  a 
  broad 
  oval 
  form 
  ; 
  it 
  occupies 
  little 
  more 
  than 
  

   the 
  central 
  J 
  of 
  the 
  canal. 
  The 
  free 
  subumbrellar 
  edges 
  of 
  the 
  

   folds 
  are 
  neither 
  scalloped, 
  as 
  Haeckel 
  represented 
  them, 
  nor 
  per- 
  

   fectly 
  smooth, 
  as 
  in 
  A. 
  Agassiz's 
  figure, 
  but 
  sometimes 
  smooth, 
  some- 
  

   times 
  irregularly 
  wavy 
  or 
  lobed; 
  that 
  is, 
  they 
  are 
  intermediate 
  

   between 
  the 
  two 
  extremes, 
  as 
  were 
  Linko's 
  examples 
  from 
  Barents 
  

   Sea. 
  

  

  A 
  much 
  contracted 
  specimen, 
  now 
  about 
  30 
  mm. 
  in 
  diameter, 
  has 
  

   younger 
  gonads, 
  with 
  only 
  about 
  15 
  folds 
  on 
  each 
  side, 
  and 
  the 
  folds 
  

   so 
  much 
  shorter 
  that 
  the 
  whole 
  organ 
  is 
  lanceolate. 
  A 
  still 
  earlier 
  

   stage 
  is 
  to 
  be 
  seen 
  in 
  the 
  specimen 
  from 
  station 
  4793, 
  likewise 
  30 
  mm. 
  

   in 
  diameter, 
  but 
  fully 
  expanded, 
  so 
  that 
  this 
  is 
  about 
  life 
  size, 
  and 
  

   this 
  specimen 
  is 
  especially 
  instructive, 
  for 
  two 
  of 
  the 
  gonads 
  illus- 
  

   trate 
  as 
  many 
  successive 
  steps 
  in 
  development. 
  In 
  the 
  younger 
  

   the 
  radial 
  canal 
  is 
  somewhat 
  dilated 
  in 
  the 
  region 
  of 
  the 
  future 
  sex 
  

   organ, 
  and 
  there 
  are 
  eight 
  or 
  nine 
  short 
  lateral 
  branches 
  on 
  each 
  side 
  — 
  

   the 
  proximal 
  ones 
  minute, 
  the 
  more 
  distal 
  longer. 
  The 
  gonad 
  tissue 
  

   is, 
  so 
  far, 
  only 
  a 
  slight 
  thickening 
  of 
  the 
  walls 
  of 
  the 
  diverticula. 
  

   In 
  a 
  further 
  developed 
  gonad 
  there 
  are 
  about 
  twice 
  as 
  many 
  lateral 
  

   branches 
  on 
  each 
  side 
  of 
  the 
  radial 
  canal, 
  the 
  ones 
  in 
  the 
  middle 
  

   being 
  the 
  longest, 
  the 
  proximal 
  ones 
  obviously 
  more 
  recently 
  formed, 
  

   and 
  the 
  sexual 
  thickenings 
  now 
  extend 
  from 
  the 
  distal 
  end 
  to 
  the 
  mid- 
  

   region. 
  

  

  Tentacles 
  and 
  cordyli. 
  — 
  In 
  the 
  youngest 
  specimen 
  there 
  are 
  13, 
  11, 
  

   and 
  9 
  subradial 
  tentacles, 
  in 
  three 
  successive 
  quadrants 
  — 
  that 
  is, 
  a 
  

   total 
  of 
  about 
  50; 
  and 
  from 
  1-8, 
  usually 
  4 
  or 
  5, 
  cordyli 
  between 
  each 
  

   pair 
  of 
  tentacles, 
  mth 
  about 
  40 
  in 
  the 
  only 
  quadrant 
  in 
  which 
  they 
  

   could 
  be 
  counted, 
  or 
  a 
  total 
  of 
  about 
  160. 
  In 
  the 
  somewhat 
  older 
  

   specimen 
  with 
  intermediate 
  gonads 
  there 
  are 
  11 
  and 
  16 
  tentacles 
  in 
  

   two 
  quadrants, 
  and 
  in 
  the 
  latter 
  the 
  tentacles 
  are 
  crowded. 
  In 
  the 
  

   largest 
  and 
  oldest 
  specimen 
  the 
  number 
  of 
  tentacles 
  is 
  much 
  greater. 
  

   In 
  two 
  quadrants 
  there 
  are 
  27 
  and 
  32 
  — 
  that 
  is, 
  a 
  probable 
  total 
  of 
  

   about 
  125, 
  of 
  various 
  sizes, 
  some 
  obviously 
  very 
  young; 
  and 
  the 
  

   presence 
  of 
  a 
  considerable 
  number 
  of 
  minute 
  tentacular 
  knobs 
  sug- 
  

   gests 
  that 
  a 
  much 
  greater 
  number 
  of 
  tentacles 
  would 
  have 
  been 
  

   attained 
  eventually. 
  There 
  are 
  from 
  1-3, 
  often 
  2, 
  cordyli 
  between 
  

   every 
  two 
  tentacles 
  or 
  knobs; 
  thus 
  the 
  number 
  of 
  cordyli 
  does 
  not 
  

   keep 
  pace 
  in 
  its 
  increase 
  with 
  that 
  of 
  tentacles. 
  In 
  Haeckel's 
  speci- 
  

   mens, 
  50-60 
  mm. 
  in 
  diameter 
  in 
  alcohol, 
  but 
  no 
  doubt 
  still 
  larger 
  in 
  

   life, 
  there 
  were 
  200-300 
  tentacles, 
  with 
  about 
  the 
  same 
  number 
  of 
  

   cordyli; 
  and 
  in 
  the 
  large 
  examples 
  described 
  by 
  A. 
  Agassiz 
  (1865) 
  

   the 
  cordyli 
  alternate 
  with 
  the 
  very 
  numerous 
  tentacles. 
  

  

  