﻿NO. 
  1946. 
  PACIFIC 
  MEDUSAE 
  AND 
  SIPIIONOPIIORAE—BIGELOW. 
  13 
  

  

  stance 
  is 
  extremely 
  thick 
  and 
  tough, 
  the 
  bell 
  almost 
  spherical, 
  but 
  in 
  

   all 
  of 
  our 
  specimens 
  slightly 
  broader 
  than 
  high. 
  The 
  bell 
  cavity 
  is 
  

   subcylindrical, 
  one-half 
  to 
  one-third 
  higher 
  than 
  broad, 
  the 
  subum- 
  

   brella 
  densely 
  pigmented, 
  with 
  the 
  jelly 
  very 
  transparent; 
  the 
  speci- 
  

   men 
  looks 
  like 
  a 
  vitreous 
  ball 
  with 
  its 
  center 
  occupied 
  by 
  an 
  opaque 
  

   plug 
  (pi. 
  1, 
  fig. 
  1). 
  The 
  entire 
  animal, 
  at 
  least 
  after 
  preservation, 
  is 
  

   so 
  tough 
  and 
  resistant 
  that 
  it 
  will 
  bear 
  handling 
  even 
  when 
  removed 
  

   from 
  its 
  fluid. 
  

  

  Manubrium. 
  — 
  The 
  manubrium 
  is 
  short, 
  reaching 
  hardly 
  to 
  the 
  mid- 
  

   level 
  of 
  the 
  bell 
  cavity; 
  the 
  mouth 
  is 
  surrounded 
  by 
  four 
  separate 
  

   lips, 
  with 
  slightly 
  fimbriated 
  margins 
  (pi. 
  1, 
  fig. 
  3). 
  In 
  the 
  large 
  

   specimens 
  the 
  manubrium 
  is 
  attached 
  to 
  the 
  subumbrella 
  along 
  each 
  

   radius, 
  as 
  in 
  other 
  Pandeids, 
  only 
  here 
  to 
  an 
  extreme 
  degree, 
  the 
  lines 
  

   of 
  attachment 
  extending 
  downward 
  as 
  far 
  as 
  the 
  sexual 
  products 
  are 
  

   developed. 
  

  

  Gonads. 
  — 
  In 
  a 
  specimen 
  17 
  mm. 
  high 
  the 
  gonads 
  consist 
  of 
  eight 
  

   adradial 
  masses, 
  oval 
  in 
  outline, 
  broadest 
  at 
  their 
  lower 
  ends. 
  The 
  

   sexual 
  tissue 
  is, 
  of 
  course, 
  discontinuous 
  in 
  the 
  perradii, 
  where 
  there 
  

   is 
  a 
  broad 
  band, 
  reaching 
  to 
  the 
  base 
  of 
  the 
  manubrium, 
  along 
  which 
  

   no 
  sexual 
  products 
  are 
  present 
  (pi. 
  1, 
  fig. 
  3). 
  The 
  specimen 
  in 
  

   question 
  is 
  a 
  female, 
  with 
  large 
  ova. 
  The 
  precise 
  outlines 
  of 
  the 
  sex- 
  

   ual 
  masses 
  are 
  easily 
  followed, 
  because 
  their 
  whiteness 
  contrasts 
  very 
  

   strongly 
  with 
  the 
  dense, 
  almost 
  opaque 
  endodermic 
  pigmenta- 
  

   tion 
  of 
  all 
  other 
  parts 
  of 
  the 
  walls 
  of 
  the 
  manubrium. 
  In 
  the 
  small- 
  

   est 
  specimen 
  the 
  manubrium 
  is 
  much 
  contracted, 
  and 
  consequently 
  

   the 
  gonads 
  folded 
  and 
  crumpled, 
  and 
  in 
  this 
  case 
  the 
  adradial 
  gonads 
  

   of 
  each 
  pair 
  are 
  close 
  together 
  near 
  the 
  bases, 
  though 
  still 
  distinctly 
  

   separate 
  in 
  the 
  interradius. 
  

  

  The 
  question 
  whether 
  the 
  pairs 
  of 
  adradial 
  gonads 
  are 
  the 
  arms 
  of 
  

   organs 
  originally 
  horseshoe-shaped 
  and 
  secondarily 
  separated 
  by 
  the 
  

   growth 
  of 
  the 
  manubrium 
  remains 
  unanswered, 
  but 
  the 
  probability 
  is 
  

   that 
  they 
  are. 
  In 
  a 
  large 
  male 
  the 
  gonads 
  agree 
  very 
  well 
  with 
  those 
  

   of 
  the 
  female 
  described 
  above. 
  

  

  Canal 
  system. 
  — 
  The 
  margins 
  of 
  the 
  canals, 
  both 
  radial 
  and 
  circular, 
  

   are 
  smooth, 
  but 
  in 
  most 
  of 
  the 
  specimens 
  there 
  is 
  a 
  slight 
  dilation 
  of 
  

   the 
  radial 
  canals 
  marking 
  the 
  level 
  of 
  the 
  lower 
  end 
  of 
  the 
  perradial 
  

   attachment 
  of 
  manubrium 
  to 
  subumbrella. 
  In 
  one 
  example 
  the 
  

   margins 
  of 
  the 
  canals 
  are 
  jagged 
  at 
  this 
  point. 
  

  

  Tentacles. 
  — 
  The 
  arrangement 
  of 
  tentacles 
  is 
  characteristic, 
  there 
  

   being 
  four 
  large 
  perradials 
  and 
  a 
  considerable 
  number 
  of 
  much 
  

   smaller 
  interradials 
  (pi. 
  1, 
  fig. 
  2). 
  As 
  in 
  Heterotiara 
  and 
  Calycopsis 
  

   the 
  basal 
  ends 
  of 
  the 
  radials 
  lie 
  in 
  furrows 
  of 
  the 
  exumbrella; 
  and 
  the 
  

   tentacles 
  turn 
  outward 
  a 
  short 
  distance 
  above 
  the 
  margin. 
  The 
  

   interradials, 
  however, 
  spring 
  directly 
  from 
  the 
  margin, 
  not 
  touching 
  

   the 
  exumbrella. 
  None 
  have 
  terminal 
  dilations 
  of 
  any 
  kind, 
  nor 
  are 
  

  

  