﻿12 
  PROCEEDINGS 
  OF 
  THE 
  NATIONAL. 
  MUSEUM 
  vou 
  67 
  

  

  Thoracic 
  appendages. 
  — 
  There 
  are 
  now 
  11 
  or 
  12 
  swimming 
  hairs. 
  

   All 
  of 
  the 
  thoracic 
  appendages 
  are 
  developed 
  and 
  the 
  segments 
  of 
  

   each 
  are 
  evident. 
  Gill 
  buds 
  appear 
  on 
  the 
  third 
  maxilliped 
  and 
  the 
  

   first 
  and 
  second 
  pereiopods. 
  

  

  Abdomen. 
  — 
  The 
  lateral 
  spines 
  of 
  the 
  third, 
  fourth, 
  and 
  fifth 
  seg- 
  

   ments 
  are 
  greatly 
  elongated. 
  The 
  abdominal 
  appendages 
  are 
  elon- 
  

   gated 
  and 
  biramous. 
  

  

  FIRST 
  MEGALOFS 
  (fig. 
  129) 
  

  

  After 
  the 
  molt 
  from 
  the 
  last 
  zoeal 
  stage, 
  the 
  form 
  of 
  the 
  car- 
  

   apace 
  is 
  almost 
  completely 
  changed. 
  The 
  dorsal 
  and 
  lateral 
  spines 
  

   are 
  lost. 
  The 
  rostral 
  spine 
  has 
  disappeared 
  and 
  two 
  small 
  frontal 
  

   spines 
  protrude 
  from 
  the 
  anterior 
  border 
  of 
  the 
  carapace. 
  The 
  perei- 
  

   opods 
  are 
  fully 
  developed 
  and 
  the 
  abdominal 
  appendages 
  are 
  power- 
  

   ful 
  swimming 
  organs. 
  The 
  sense 
  organs 
  are 
  all 
  well 
  developed 
  in 
  

   consonance 
  with 
  the 
  more 
  independent 
  habits 
  of 
  the 
  megalops. 
  

  

  Cephalic 
  appendages. 
  — 
  The 
  antennule 
  (fig. 
  135) 
  is 
  now 
  well 
  

   formed. 
  Its 
  basal 
  segment 
  is 
  greatly 
  enlarged 
  and 
  contains 
  the 
  

   statocyst. 
  Distally 
  its 
  two 
  rami 
  appear 
  as 
  short 
  flagella 
  that 
  carry 
  

   numerous 
  sensory 
  hairs. 
  

  

  The 
  antenna 
  (fig. 
  135) 
  assumes 
  what 
  is 
  practically 
  the 
  adult 
  con- 
  

   dition. 
  The 
  tremendous 
  spine 
  of 
  the 
  zoea 
  disappears 
  completely 
  as 
  

   does 
  also 
  the 
  minute 
  exopodite. 
  The 
  endopodite 
  remains 
  as 
  a 
  slender, 
  

   many 
  jointed 
  flagellum 
  that 
  is 
  sparsely 
  hairy 
  at 
  the 
  joints. 
  

  

  The 
  mandible 
  (fig. 
  138) 
  also 
  assumes 
  the 
  adult 
  condition. 
  The 
  

   palp 
  is 
  divided 
  into 
  three 
  segments, 
  each 
  of 
  which 
  bears 
  a 
  few 
  hairs. 
  

  

  The 
  maxillule 
  (fig. 
  140 
  and 
  the 
  maxilla 
  (fig. 
  143) 
  begin 
  to 
  de- 
  

   generate 
  at 
  this 
  stage. 
  Their 
  endopodites 
  begin 
  to 
  lose 
  their 
  joints 
  

   and 
  hairs. 
  

  

  Thoracic 
  appendages. 
  — 
  The 
  maxillipeds 
  undergo 
  a 
  very 
  striking 
  

   transformation. 
  They 
  are 
  no 
  longer 
  swimming 
  organs, 
  but 
  are 
  

   changed 
  into 
  masticatory 
  appendages 
  with 
  sensory 
  palps. 
  

  

  The 
  first 
  maxilliped 
  (fig. 
  145) 
  shows 
  these 
  typical 
  changes. 
  The 
  

   exopodite 
  becomes 
  relatively 
  smaller 
  and 
  permanently 
  flexed 
  near 
  its 
  

   middle. 
  Its 
  distal 
  portion 
  becomes 
  a 
  short 
  flagellum 
  and 
  i£ 
  carries 
  

   several 
  small 
  hairs 
  at 
  its 
  tip. 
  The 
  endopodite 
  loses 
  its 
  joints 
  and 
  

   becomes 
  adapted 
  for 
  mastication. 
  The 
  lobes 
  of 
  the 
  basipodite 
  are 
  

   enlarged 
  and 
  adapted 
  for 
  mastication. 
  A 
  large 
  epipodite 
  is 
  present. 
  

  

  The 
  second 
  maxilliped 
  (fig. 
  146) 
  has 
  an 
  exopodite 
  like 
  the 
  first. 
  

   The 
  endopodite 
  shows 
  five 
  segments. 
  The 
  basipodite 
  carries 
  a 
  small 
  

   epipodite 
  and 
  a 
  gill 
  bud. 
  

  

  The 
  third 
  maxilliped 
  now 
  becomes 
  the 
  largest 
  of 
  the 
  three. 
  Its 
  

   exopodite 
  is 
  like 
  that 
  of 
  the 
  first 
  and 
  second. 
  The 
  endopodite 
  is 
  

   greatly 
  enlarged 
  and 
  consists 
  of 
  six 
  segments. 
  The 
  proximal 
  three 
  

   are 
  large 
  and 
  flattened 
  and 
  form 
  an 
  operculum, 
  while 
  the 
  distal 
  three 
  

  

  