﻿art. 
  3 
  STUDIES 
  ON 
  LARVAE 
  OF 
  CRABS 
  HYMAN 
  5 
  

  

  second 
  zoea 
  (figs. 
  45 
  and 
  46) 
  

  

  According 
  to 
  Birge, 
  the 
  zoea 
  molts 
  a 
  large 
  number 
  of 
  times 
  before 
  

   it 
  reaches 
  the 
  condition 
  designated 
  as 
  the 
  second 
  zoeal 
  stage. 
  While 
  

   my 
  observations 
  are 
  not 
  numerous 
  enough 
  to 
  justify 
  a 
  dogmatic 
  

   statement, 
  I 
  have 
  not 
  found 
  this 
  to 
  be 
  the 
  case. 
  Each 
  of 
  the 
  first 
  

   zoeas 
  under 
  my 
  observation 
  became 
  transformed 
  into 
  a 
  second-stage 
  

   zoea 
  at 
  the 
  first 
  molt. 
  

  

  Cephalothorax. 
  — 
  The 
  dorsal 
  and 
  rostral 
  spines 
  are 
  longer 
  and 
  

   more 
  slender. 
  The 
  eyes 
  are 
  movable. 
  

  

  Cephalic 
  appendages. 
  — 
  The 
  antennae 
  (fig. 
  60) 
  are 
  longer 
  and 
  

   more 
  slender. 
  The 
  maxillae 
  (fig. 
  56) 
  show 
  changes 
  in 
  the 
  scaphog- 
  

   nathite, 
  which 
  is 
  now 
  a 
  flattened 
  plate 
  with 
  hairs 
  along 
  its 
  border. 
  

  

  Thoracic 
  appendages. 
  — 
  The 
  number 
  of 
  swimming 
  hairs 
  on 
  the 
  

   first 
  and 
  second 
  maxillipeds 
  (figs. 
  64 
  and 
  68) 
  is 
  now 
  six 
  or 
  seven. 
  

   The 
  third 
  maxillipeds 
  are 
  larger 
  and, 
  at 
  their 
  distal 
  ends, 
  cleft 
  

   into 
  exopodite 
  and 
  endopodite. 
  The 
  chelipeds 
  also 
  show 
  cleft 
  ex- 
  

   tremities. 
  The 
  buds 
  of 
  the 
  remaining 
  pereiopods 
  are 
  easily 
  iden- 
  

   tified. 
  

  

  Abdomen. 
  — 
  The 
  lateral 
  spinous 
  processes 
  on 
  the 
  segments 
  are 
  

   somewhat 
  more 
  pronounced. 
  The 
  anlagen 
  of 
  the 
  abdominal 
  ap- 
  

   pendages 
  are 
  visible 
  beneath 
  the 
  cuticle 
  but 
  do 
  not 
  yet 
  form 
  protru- 
  

   sions. 
  The 
  cornua 
  of 
  the 
  telson 
  (fig. 
  73) 
  are 
  further 
  elongated. 
  

  

  third 
  zoea 
  (figs. 
  47 
  and 
  49) 
  

  

  Again 
  Birge 
  states 
  that 
  several 
  molts 
  occur 
  before 
  the 
  third 
  

   zoeal 
  stage 
  is 
  reached 
  but 
  my 
  observations 
  indicate 
  that 
  the 
  second 
  

   zoea 
  becomes 
  a 
  third-stage 
  zoea 
  at 
  the 
  first 
  molt. 
  

  

  While 
  the 
  earlier 
  zoeas 
  are 
  taken 
  in 
  large 
  numbers 
  at 
  the 
  surface 
  

   of 
  the 
  water, 
  the 
  third-stage 
  form 
  is 
  rather 
  rare. 
  It 
  is 
  taken 
  in 
  

   small 
  numbers 
  both 
  from 
  the 
  surface 
  and 
  from 
  near 
  the 
  bottom. 
  

   It 
  doubtless 
  has 
  difficulty 
  in 
  maintaining 
  itself 
  at 
  the 
  surface 
  on 
  

   account 
  of 
  its 
  increased 
  weight. 
  

  

  Cephalothorax. 
  — 
  The 
  dorsal 
  and 
  rostral 
  spines 
  are 
  again 
  longer 
  

   and 
  relatively 
  more 
  slender. 
  The 
  eyes 
  are 
  more 
  freely 
  movable 
  and 
  

   are 
  relatively 
  larger. 
  

  

  Cephalic 
  appendages. 
  —The 
  antennules 
  (fig. 
  39) 
  are 
  appreciably 
  

   larger 
  and 
  are 
  superficially 
  constricted 
  near 
  the 
  base. 
  The 
  antennae 
  

   (fig. 
  61) 
  are 
  longer 
  and 
  more 
  slender. 
  Each 
  shows 
  now 
  the 
  anlage 
  

   of 
  the 
  flagellum 
  of 
  the 
  permanent 
  antenna. 
  This 
  appears 
  as 
  a 
  bud 
  

   between 
  the 
  exopodite 
  and 
  the 
  spine. 
  The 
  maxillule 
  (fig. 
  53) 
  shows 
  

   a 
  minute 
  but 
  significant 
  change 
  — 
  a 
  single 
  epipodal 
  hair 
  appears 
  on 
  

   ' 
  the 
  basipodite. 
  

  

  Thoracic 
  appendages. 
  — 
  The 
  swimming 
  hairs 
  are 
  now 
  eight 
  or 
  nine. 
  

   The 
  exopodites 
  of 
  the 
  first 
  and 
  second 
  maxillipeds 
  (figs. 
  65 
  and 
  69) 
  

  

  