﻿NO. 
  1950. 
  CRUSTACEAN 
  PARASITES 
  OF 
  FISH 
  AND 
  CRABS— 
  WILSON. 
  253 
  

  

  lips 
  are 
  prolonged 
  and 
  loosely 
  united 
  into 
  a 
  sort 
  of 
  proboscis, 
  and 
  

   the 
  mandibles 
  form 
  swellings 
  at 
  its 
  sides. 
  

  

  Just 
  behind 
  the 
  head 
  are 
  four 
  pairs 
  of 
  rudimentary 
  legs, 
  so 
  close 
  

   together 
  that 
  they 
  overlap 
  for 
  two-thirds 
  of 
  their 
  length. 
  Each 
  leg 
  

   consists 
  of 
  a 
  broad 
  triangular 
  lamina, 
  representing 
  the 
  basal 
  joint, 
  

   and 
  two 
  tiny 
  spines, 
  representing 
  the 
  rami. 
  In 
  the 
  developmental 
  

   stage 
  they 
  stand 
  out 
  nearly 
  at 
  right 
  angles 
  to 
  the 
  ventral 
  surface, 
  in 
  

   the 
  adult 
  they 
  are 
  tightly 
  appressed 
  to 
  that 
  surface. 
  The 
  first 
  four 
  

   (leg-bearing) 
  thorax 
  segments 
  are 
  narrow 
  and 
  neck-like 
  and 
  very 
  

   short; 
  the 
  fifth 
  segment 
  is 
  of 
  the 
  same 
  width 
  and 
  greatly 
  elongated, 
  

   and 
  forms 
  the 
  bulk 
  of 
  the 
  so-called 
  neck; 
  the 
  genital 
  segment 
  is 
  

   enlarged 
  to 
  two 
  or 
  three 
  times 
  the 
  diameter 
  of 
  the 
  neck, 
  varying 
  

   considerably 
  in 
  different 
  individuals. 
  It 
  is 
  impossible 
  in 
  this 
  species 
  

   to 
  locate 
  accurately 
  the 
  tlividing 
  line 
  between 
  the 
  fifth 
  and 
  genital 
  

   segments, 
  but 
  judging 
  from 
  the 
  following 
  species 
  the 
  point 
  where 
  

   the 
  enlargement 
  begins 
  is 
  the 
  line 
  of 
  demarcation. 
  

  

  At 
  about 
  the 
  center 
  of 
  the 
  enlarged 
  genital 
  segment 
  the 
  body 
  h 
  

   bent 
  abruptly 
  so 
  that 
  the 
  abdomen 
  points 
  toward 
  the 
  head. 
  

  

  In 
  the 
  developmental 
  stages 
  the 
  curve 
  is 
  broad 
  and 
  there 
  is 
  but 
  

   little 
  twisting 
  of 
  the 
  body; 
  in 
  the 
  mature 
  adult 
  the 
  curve 
  becomes 
  

   so 
  sharp 
  that 
  the 
  dorsal 
  surface 
  of 
  the 
  abdomen 
  is 
  brought 
  almost 
  

   into 
  actual 
  contact 
  with 
  the 
  side 
  of 
  the 
  fifth 
  segment. 
  At 
  the 
  same 
  

   time, 
  the 
  posterior 
  portion 
  of 
  the 
  body 
  is 
  twisted 
  to 
  the 
  right 
  or 
  left, 
  

   so 
  that 
  the 
  legs 
  and 
  mouth-parts 
  appear 
  to 
  be 
  on 
  one 
  of 
  the 
  lateral 
  

   surfaces. 
  

  

  The 
  abdomen 
  ^ 
  long 
  and 
  slender, 
  and 
  tapers 
  gradually 
  from 
  base 
  

   to 
  tip; 
  at 
  the 
  base 
  it 
  is 
  about 
  half 
  the 
  diameter 
  of 
  the 
  genital 
  seg- 
  

   ment, 
  and 
  on 
  a 
  level 
  with 
  the 
  dorsal 
  surface 
  of 
  the 
  latter. 
  It 
  shows 
  

   no 
  external 
  signs 
  of 
  segmentation. 
  On 
  the 
  sides 
  of 
  the 
  genital 
  seg- 
  

   ment 
  at 
  the 
  posterior 
  end 
  are 
  two 
  pairs 
  of 
  dichotomously 
  branched 
  

   processes, 
  and 
  along 
  the 
  lateral 
  margins 
  of 
  the 
  abdomen 
  are 
  seven 
  

   or 
  eight 
  additional 
  pairs. 
  At 
  fii'st 
  these 
  are 
  short 
  and 
  simple 
  and 
  

   do 
  not 
  conceal 
  the 
  surrounding 
  parts, 
  but 
  they 
  increase 
  in 
  size 
  and 
  

   complexity 
  with 
  age, 
  and 
  finally 
  cover 
  and 
  conceal 
  the 
  abdomen, 
  

   egg-strings, 
  and 
  posterior 
  portion 
  of 
  the 
  genital 
  segment. 
  

  

  The 
  egg-strings 
  are 
  scarcely 
  wider 
  than 
  one 
  of 
  the 
  processes, 
  but 
  

   are 
  from 
  one 
  and 
  a 
  half 
  to 
  two 
  times 
  the 
  length 
  of 
  the 
  body. 
  Each 
  

   is 
  tightly 
  and 
  irregularly, 
  coiled 
  into 
  a 
  small 
  mass, 
  entirely 
  sur- 
  

   rounded 
  by 
  the 
  processes, 
  and 
  in 
  this 
  way 
  supported 
  and 
  protected. 
  

  

  Color 
  of 
  the 
  entire 
  body 
  blood- 
  or 
  wine-red, 
  even 
  to 
  the 
  tips 
  of 
  the 
  

   horns; 
  dichotomous 
  processes 
  pale 
  yellow-gray 
  or 
  straw-color; 
  egg- 
  

   strings 
  snow-white. 
  

  

  Total 
  length, 
  20 
  mm. 
  Length 
  of 
  horns, 
  5 
  mm.; 
  of 
  processes, 
  6 
  

   mm. 
  Diameter 
  of 
  head, 
  2.8 
  mm. 
  ; 
  of 
  neck, 
  1 
  mm. 
  ; 
  of 
  genital 
  segment, 
  

   2.8 
  mm. 
  

  

  