﻿82 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  vol.44. 
  

  

  ber 
  of 
  stalked 
  nematocyst 
  knobs 
  on 
  the 
  tentacles, 
  the 
  more 
  complexly 
  

   branched 
  limbar 
  canals, 
  and 
  the 
  fewer 
  open 
  stigmata. 
  

  

  In 
  the 
  eastern 
  Pacific 
  specimens 
  50-55 
  mm. 
  in 
  diameter, 
  the 
  tuber- 
  

   cles 
  were 
  extremely 
  prominent 
  and 
  covered 
  all 
  the 
  upper 
  surface 
  of 
  

   the 
  disk 
  except 
  a 
  narrow 
  marginal 
  ring 
  (1911&, 
  pi. 
  28, 
  fig. 
  1). 
  In 
  the 
  

   present 
  specimens 
  of 
  25-40 
  mm. 
  they 
  are 
  smaller 
  and 
  restricted 
  to 
  

   the 
  central 
  part 
  of 
  the 
  disk. 
  But 
  the 
  fact 
  that 
  in 
  one 
  of 
  28 
  mm. 
  the 
  

   region 
  which 
  they 
  cover 
  is 
  only 
  as 
  broad 
  as 
  half 
  the 
  radius 
  of 
  the 
  

   disk, 
  whereas 
  in 
  one 
  of 
  35 
  mm. 
  it 
  is 
  as 
  broad 
  as 
  the 
  radius, 
  shows 
  

   that 
  they 
  extend 
  farther 
  and 
  farther 
  toward 
  the 
  margin 
  with 
  growth, 
  

   a 
  later 
  stage 
  in 
  this 
  process 
  being 
  illustrated 
  by 
  the 
  large 
  specimens 
  

   from 
  the 
  eastern 
  Pacific. 
  Specimens 
  of 
  11 
  mm. 
  or 
  less 
  have 
  no 
  

   tubercles, 
  and 
  there 
  is 
  a 
  gap 
  in 
  the 
  series 
  between 
  them 
  and 
  those 
  

   of 
  23 
  mm. 
  

  

  The 
  number 
  of 
  tentacular 
  nematocysts 
  in 
  each 
  row, 
  in 
  five 
  tentacles 
  

   taken 
  at 
  random 
  from 
  three 
  specimens, 
  is: 
  25 
  mm. 
  in 
  diameter 
  — 
  30, 
  

   19, 
  19; 
  27, 
  19, 
  19; 
  29, 
  19, 
  19; 
  31, 
  19, 
  19; 
  31, 
  18, 
  19; 
  31, 
  17, 
  16 
  

   30 
  mm. 
  in 
  diameter— 
  25, 
  15, 
  16; 
  30, 
  19, 
  18; 
  27, 
  15, 
  16; 
  26, 
  18, 
  18 
  

   27, 
  16, 
  17; 
  40 
  mm. 
  in 
  diameter— 
  32, 
  16, 
  16; 
  29, 
  14, 
  15; 
  34, 
  15, 
  15 
  

   30, 
  17, 
  16; 
  31, 
  17, 
  16. 
  

  

  At 
  first 
  sight 
  it 
  seems 
  surprising 
  that 
  the 
  smallest 
  specimens 
  

   should 
  have 
  more 
  knobs 
  than 
  the 
  next 
  larger 
  one, 
  but 
  it 
  has 
  a 
  goose- 
  

   barnacle 
  parasitic 
  upon 
  it, 
  and 
  is 
  perhaps 
  stunted 
  in 
  consequence. 
  

   The 
  numbers 
  in 
  all 
  three 
  are 
  rather 
  larger 
  than 
  in 
  the 
  eastern 
  Pacific 
  

   specimens, 
  in 
  which 
  they 
  were 
  from 
  25-29 
  in 
  each 
  of 
  the 
  long 
  and 
  

   11-14 
  in 
  each 
  of 
  the 
  short 
  rows. 
  

  

  Umhella 
  has 
  been 
  described 
  as 
  having 
  9-12 
  in 
  the 
  long, 
  6-8 
  in 
  the 
  

   short 
  rows 
  (A. 
  Agassiz, 
  1883; 
  Chun, 
  18976). 
  In 
  two 
  specimens 
  the 
  

   numbers 
  are: 
  22 
  mm. 
  in 
  diameter, 
  Naples 
  — 
  12, 
  6, 
  7; 
  11, 
  6, 
  6; 
  12, 
  

   7, 
  7; 
  10, 
  6, 
  6; 
  11, 
  5, 
  6; 
  26 
  mm. 
  in 
  diameter, 
  Tortugas— 
  13, 
  9, 
  7; 
  11, 
  

   6, 
  7; 
  15, 
  7, 
  8; 
  11, 
  9, 
  9; 
  12, 
  6, 
  8. 
  Unfortunately, 
  I 
  have 
  no 
  large 
  

   specimens 
  with 
  the 
  tentacles 
  intact. 
  

  

  The 
  limbar 
  canals 
  in 
  the 
  Japanese 
  specimens 
  agree 
  very 
  well 
  with 
  

   the 
  conditions 
  in 
  the 
  eastern 
  Pacific 
  series 
  (191 
  1&), 
  being 
  very 
  much 
  

   branched 
  and 
  irregular, 
  and 
  the 
  limbus 
  itself 
  is 
  narrower 
  than 
  in 
  

   any 
  umhella 
  which 
  I 
  have 
  seen, 
  though 
  it 
  would 
  take 
  a 
  large 
  series 
  

   of 
  each 
  to 
  show 
  whether 
  this 
  difference 
  is 
  really 
  important. 
  In 
  the 
  

   specimens 
  of 
  pacijica 
  upward 
  of 
  25 
  mm. 
  in 
  diameter 
  there 
  are 
  no 
  

   open 
  stigmata 
  in 
  the 
  central 
  region, 
  but 
  in 
  the 
  peripheral 
  parts 
  of 
  

   the 
  disk 
  the 
  stigmata 
  are 
  rather 
  more 
  numerous 
  than 
  in 
  the 
  corre- 
  

   sponding 
  region 
  in 
  large 
  eastern 
  Pacific 
  examples, 
  from 
  which 
  it 
  

   appears 
  that 
  they 
  are 
  successively 
  closed 
  as 
  growth 
  progresses. 
  In 
  

   umbella 
  many 
  more 
  are 
  permanently 
  open 
  (191 
  1&). 
  The 
  very 
  small 
  

   specimens 
  1.5-2 
  mm. 
  broad 
  are 
  all 
  further 
  advanced 
  than 
  the 
  larva 
  

   which 
  I 
  have 
  already 
  described, 
  though 
  no 
  larger, 
  for 
  all 
  of 
  them 
  

   have 
  more 
  than 
  eight 
  gastrozooids, 
  and 
  the 
  velum 
  is 
  already 
  notice- 
  

   able 
  in 
  all. 
  

  

  