﻿32 
  riiOCBJEDINGS 
  OF 
  THE 
  NATIONAL 
  MUSEUM. 
  vol.44. 
  

  

  Genus 
  TIAROPSIS 
  L. 
  Agassiz. 
  

  

  The 
  species 
  of 
  Tiaropsis 
  fall 
  into 
  two 
  distinct 
  groups, 
  one 
  wdth 
  very 
  

   numerous 
  tentacles 
  all 
  alike, 
  the 
  other 
  with 
  four 
  or 
  eight 
  large 
  tenta- 
  

   cles 
  and 
  a 
  considerable 
  number 
  of 
  rudimentary 
  subradial 
  tentacular 
  

   bulbs. 
  The 
  latter 
  group 
  consists 
  of 
  rosea 
  Agassiz 
  and 
  Mayer, 
  

   mediterranea 
  Metschnikoff, 
  and 
  Icelseyi 
  Torrey, 
  all 
  of 
  them 
  tropical 
  

   or 
  at 
  least 
  warm 
  water 
  forms, 
  which 
  therefore 
  need 
  not 
  concern 
  us 
  here. 
  

   The 
  first 
  group, 
  comprising 
  diademata 
  L. 
  Agassiz, 
  multicirrhata 
  

   Sars, 
  maclayi 
  von 
  Lendenfcld, 
  and 
  davisii 
  Browne, 
  belongs 
  to 
  the 
  

   colder 
  waters 
  of 
  both 
  hemispheres, 
  and 
  its 
  members 
  are 
  very 
  closely 
  

   allied 
  to 
  one 
  another. 
  Diademata 
  and 
  multicirrhata 
  are 
  separated 
  

   only 
  by 
  the 
  fact 
  that 
  ocelli 
  are 
  said 
  to 
  be 
  present 
  in 
  the 
  latter, 
  absent 
  

   in 
  the 
  former. 
  (For 
  details, 
  see 
  Mayer, 
  1910, 
  p. 
  259.) 
  The 
  fact 
  that 
  

   diademata 
  lacks 
  tentacular 
  ocelli 
  has 
  been 
  established 
  on 
  great 
  num- 
  

   bers 
  of 
  specimens, 
  but 
  the 
  tentacular 
  bulbs 
  are 
  not 
  altogether 
  without 
  

   pigment, 
  for 
  in 
  all 
  the 
  numerous 
  specimens 
  which 
  I 
  have 
  studied 
  they 
  

   contain 
  a 
  small 
  amount 
  of 
  entodermic 
  pigment 
  of 
  a 
  pale 
  greenish 
  or 
  

   yello\vish-brown 
  color, 
  which 
  is 
  visible 
  only 
  when 
  the 
  animal 
  is 
  

   studied 
  against 
  a 
  white 
  background. 
  Now, 
  the 
  various 
  figures 
  of 
  the 
  

   north 
  European 
  multicirrhata 
  by 
  no 
  means 
  establish 
  the 
  presence 
  of 
  

   tentacular 
  ocelli; 
  all 
  they 
  show 
  is 
  the 
  presence 
  of 
  the 
  same 
  entodermic 
  

   pigment, 
  only 
  iii 
  much 
  denser 
  masses, 
  and 
  black 
  instead 
  of 
  pale 
  

   greenish. 
  Thus 
  the 
  distinction 
  between 
  the 
  species 
  is 
  not 
  an 
  organic 
  

   one, 
  being 
  nothing 
  but 
  a 
  question 
  of 
  the 
  density 
  and 
  color 
  of 
  the 
  pig- 
  

   ment 
  masses. 
  

  

  Under 
  these 
  circumstances 
  it 
  would 
  not 
  be 
  at 
  all 
  surprising 
  if 
  inter- 
  

   mediates 
  should 
  turn 
  up, 
  and 
  as 
  a 
  matter 
  of 
  fact 
  the 
  specimens 
  

   described 
  below 
  have 
  denser 
  tentacular 
  pigment 
  than 
  is 
  usual 
  in 
  

   diademata, 
  though 
  it 
  is 
  of 
  the 
  same 
  color. 
  On 
  the 
  whole 
  it 
  seems 
  to 
  

   me 
  likely 
  that 
  diademata 
  and 
  multicirrhata 
  are 
  the 
  extremes 
  of 
  a 
  single 
  

   varietal 
  series, 
  but 
  I 
  hesitate 
  to 
  unite 
  them 
  unequivocally 
  without 
  hav- 
  

   ing 
  had 
  an 
  opportunity 
  to 
  study 
  specimens 
  of 
  the 
  latter. 
  It 
  is 
  interest- 
  

   ing 
  in 
  this 
  connection 
  that 
  the 
  bases 
  of 
  a 
  few, 
  but 
  not 
  all, 
  of 
  the 
  tenta- 
  

   cles 
  of 
  the 
  Australian 
  T. 
  maclayi 
  are 
  pigmented. 
  It 
  is 
  impossible 
  to 
  

   determine 
  at 
  jiresent 
  just 
  what 
  relationship 
  the 
  latter 
  species 
  bears 
  to 
  

   the 
  northern 
  forms, 
  because 
  the 
  figure 
  (von 
  Lendenfcld, 
  1884, 
  pi. 
  

   23, 
  fig. 
  37) 
  is 
  diagrammatic, 
  and 
  the 
  description 
  in 
  ver}^ 
  general 
  terms. 
  

   But 
  it 
  is 
  apparently 
  distinguished 
  by 
  having 
  small, 
  instead 
  of 
  large, 
  

   crenulated 
  lips. 
  Davisii 
  is 
  apparently 
  closely 
  allied 
  to 
  maclayi, 
  but 
  

   Avithout 
  a 
  figure 
  or 
  a 
  detailed 
  description 
  I 
  hesitate 
  to 
  make 
  a 
  

   defuiite 
  assertion. 
  

  

  The 
  present 
  collection 
  contains 
  a 
  considerable 
  series 
  wliich 
  I 
  have 
  

   compared, 
  side 
  by 
  side 
  with 
  numerous 
  large 
  and 
  well-preserved 
  

  

  