﻿[13] 
  DECAPODA 
  FROM 
  ALBATROSS 
  DREDGINGS. 
  617 
  

  

  on 
  the 
  mesial 
  or 
  mesio-dorsal 
  side 
  of 
  the 
  eye-stalk, 
  somewhere 
  between 
  

   the 
  middle 
  of 
  the 
  stalk 
  and 
  the 
  cornea. 
  This 
  organ 
  is 
  very 
  highly 
  de- 
  

   veloped 
  in 
  many 
  of 
  the 
  Miersiidse 
  and 
  deep-water 
  Penaeidse, 
  appears 
  to 
  

   receive 
  a 
  branch 
  of 
  the 
  optic 
  nerve, 
  is 
  apparently 
  sensory 
  in 
  its 
  function, 
  

   and 
  has 
  sometimes 
  been 
  referred 
  to 
  as 
  a 
  phosphorescent 
  organ. 
  A 
  some- 
  

   what 
  similar, 
  though 
  very 
  small, 
  papilla 
  is 
  present 
  in 
  some 
  shallow- 
  

   water 
  Caridea 
  and 
  Schizopoda, 
  but, 
  having 
  no 
  knowledge 
  whatever 
  of 
  

   its 
  function, 
  I 
  have 
  simply 
  described 
  it, 
  in 
  the 
  list 
  of 
  abyssal 
  species 
  

   already 
  given, 
  as 
  the 
  "papilla." 
  

  

  The 
  large 
  size 
  and 
  small 
  number 
  of 
  the 
  eggs 
  is 
  a 
  very 
  marked 
  char- 
  

   acteristic 
  of 
  many 
  deep-water 
  Decapoda. 
  The 
  eggs 
  are 
  extraordinarily 
  

   large 
  in 
  several 
  species 
  of 
  Munidopsis, 
  Glyphocrangon, 
  and 
  Bythocaris, 
  

   and 
  in 
  Elasmonoius 
  inermis, 
  Sabinea 
  princeps, 
  Acanthephyra 
  gracilis, 
  and 
  

   Pasiphae 
  princeps. 
  But 
  the 
  largest 
  crustacean 
  egg 
  which 
  I 
  have 
  seen 
  

   is 
  that 
  of 
  the 
  little 
  shrimp 
  Parapasiphab' 
  sulcatifrons, 
  which 
  carries 
  only 
  

   fifteen 
  to 
  twenty 
  eggs, 
  each 
  of 
  which 
  is 
  more 
  than 
  4 
  millimeters 
  in 
  

   diameter, 
  and 
  approximately 
  equal 
  to 
  a 
  hundredth 
  of 
  the 
  bulk 
  of 
  the 
  

   animal 
  producing 
  it 
  — 
  a 
  case 
  in 
  which 
  the 
  egg 
  is 
  relatively 
  nearly 
  as 
  

   large 
  as 
  in 
  many 
  birds! 
  My 
  suggestion 
  (Amer. 
  Jour. 
  Sci., 
  II, 
  xxviii, 
  p. 
  

   50, 
  1884) 
  that 
  the 
  great 
  size 
  of 
  the 
  eggs 
  in 
  the 
  deep-water 
  Decapoda 
  

   was 
  probably 
  accompanied 
  by 
  an 
  abbreviated 
  metamorphosis 
  within 
  

   the 
  egg, 
  thus 
  producing 
  young 
  of 
  large 
  size 
  and 
  in 
  an 
  advanced 
  stage 
  

   of 
  development, 
  specially 
  fitting 
  them 
  to 
  live 
  under 
  conditions 
  similar 
  

   to 
  those 
  environing 
  the 
  adults, 
  has 
  already 
  been 
  proved 
  true 
  by 
  Prof. 
  

   G. 
  O. 
  Sars, 
  in 
  the 
  case 
  of 
  Bythocaris 
  leucopis, 
  in 
  which 
  the 
  young 
  are 
  in 
  

   a 
  stage 
  essentially 
  like 
  the 
  adult 
  before 
  leaving 
  the 
  egg. 
  ■ 
  

  

  Although 
  the 
  great 
  size 
  of 
  the 
  eggs 
  is 
  highly 
  characteristic 
  of 
  many 
  

   deep-water 
  species, 
  it 
  is 
  by 
  no 
  means 
  characteristic 
  of 
  all, 
  and, 
  as 
  the 
  

   following 
  table 
  of 
  measurements 
  shows, 
  the 
  size 
  of 
  the 
  eggs 
  has 
  no 
  defi- 
  

   nite 
  relation 
  to 
  the 
  bathymetrical 
  habitat, 
  and 
  is 
  often 
  very 
  different 
  in 
  

   closely 
  allied 
  species, 
  even 
  where 
  both 
  are 
  inhabitants 
  of 
  deep 
  water. 
  

   For 
  example, 
  the 
  eggs 
  of 
  Acanthephyra 
  gracilis 
  are 
  very 
  large, 
  while 
  

   those 
  of 
  A. 
  brevirostris 
  and 
  Agassizii 
  are 
  normally 
  small, 
  and 
  those 
  of 
  

   PontopMlus 
  abyssi 
  are 
  fully 
  as 
  small 
  as 
  in 
  the 
  comparatively 
  shallow- 
  

   water 
  species 
  of 
  the 
  genus, 
  and 
  much 
  smaller 
  than 
  those 
  of 
  many 
  shal- 
  

   low-water 
  Crangonidre. 
  

  

  For 
  the 
  purpose 
  of 
  comparing 
  the 
  size 
  of 
  theeggs 
  of 
  the 
  deep-water 
  and 
  

   shallow-water 
  species, 
  I 
  have 
  measured 
  a 
  considerable 
  number 
  of 
  Deca- 
  

   pod 
  eggs, 
  and 
  in 
  several 
  cases 
  have 
  estimated 
  approximately 
  the 
  num- 
  

   ber 
  of 
  eggs 
  carried 
  by 
  an 
  individual. 
  The 
  results 
  are 
  given 
  in 
  the 
  fol- 
  

   lowing 
  table, 
  in 
  which 
  the 
  bathymetrical 
  habitat 
  is 
  given 
  approximately 
  

   in 
  even 
  hundreds 
  of 
  fathoms, 
  habitats 
  of 
  less 
  than 
  100 
  fathoms 
  being 
  

   indicated 
  by 
  — 
  100; 
  the 
  diameter 
  is 
  the 
  approximate, 
  average 
  of 
  the 
  

   longer 
  and 
  shorter 
  diameters, 
  usually 
  of 
  several 
  eggs 
  from 
  two 
  or 
  three 
  

  

  