﻿LOBSTER 
  AND 
  CLAM 
  INVESTIGATIONS. 
  201 
  

  

  be 
  possible 
  to 
  discover 
  them 
  all 
  even 
  in 
  an 
  animal 
  whose 
  needs 
  are 
  

   so 
  simple 
  as 
  the 
  clam's, 
  but 
  a 
  similar 
  study 
  of 
  the 
  conditions 
  upon 
  

   which 
  an 
  animal's 
  life 
  depends, 
  if 
  extended 
  to 
  other 
  forms, 
  would 
  cer- 
  

   tainly 
  give 
  valuable 
  knowledge 
  in 
  many 
  cases. 
  

  

  CONDITIONS 
  CONTROLLING 
  THE 
  DISTRIBUTION 
  AND 
  GROWTH 
  

   OF 
  THE 
  YOUNG. 
  

  

  The 
  egg 
  of 
  My 
  a 
  unites 
  with 
  the 
  male 
  cell 
  in 
  the 
  water. 
  After 
  fer- 
  

   tilization 
  a 
  ciliated 
  embryo 
  is 
  produced. 
  This 
  minute 
  creature 
  swims, 
  

   and 
  probably 
  often 
  is 
  carried 
  great 
  distances 
  by 
  tide 
  currents. 
  Its 
  

   early 
  history 
  has 
  not 
  been 
  studied. 
  Even 
  after 
  developing 
  the 
  bivalve 
  

   shell 
  it 
  probably 
  swims 
  for 
  man}' 
  days 
  before 
  losing 
  its 
  cilia 
  and 
  settling 
  

   to 
  the 
  bottom. 
  The 
  swimming 
  larvae 
  may 
  sometimes 
  be 
  taken 
  in 
  great 
  

   numbers 
  in 
  a 
  skimming 
  net. 
  

  

  The 
  habits 
  of 
  the 
  young 
  of 
  Mt/a, 
  from 
  the 
  time 
  of 
  settling 
  to 
  the 
  

   bottom 
  to 
  the 
  period 
  when 
  it 
  finally 
  digs 
  into 
  the 
  soil 
  to 
  remain 
  per- 
  

   manentl}^ 
  have 
  been 
  described.'^' 
  The 
  very 
  small 
  clam 
  possesses 
  a 
  

   byssus 
  thread. 
  The 
  byssus 
  gland 
  is 
  probably 
  developed 
  at 
  the 
  time 
  

   that 
  the 
  cilia 
  are 
  lost, 
  for 
  the 
  creature 
  needs 
  this 
  organ 
  as 
  soon 
  as 
  

   swimming 
  ceases. 
  The 
  thread 
  b}^ 
  which 
  attachment 
  is 
  effected 
  was 
  

   seen 
  in 
  individuals 
  that 
  could 
  not 
  have 
  been 
  long 
  upon 
  the 
  bottom. 
  

   It 
  is 
  fixed 
  to 
  stones, 
  aquatic 
  plants, 
  and 
  other 
  objects. 
  

  

  For 
  some 
  time 
  the 
  clam 
  is 
  too 
  small 
  to 
  force 
  its 
  way 
  into 
  the 
  bottom, 
  

   though 
  it 
  early 
  and 
  persistently 
  makes 
  the 
  attempt. 
  A 
  form 
  with 
  a 
  

   shell 
  which 
  has 
  attained 
  a 
  length 
  of 
  5 
  or 
  6 
  mm. 
  is 
  able 
  to 
  burrow 
  into 
  

   almost 
  any 
  bottom. 
  From 
  the 
  first 
  the 
  byssus 
  may 
  be 
  cast 
  off 
  at 
  will, 
  

   and 
  a 
  new 
  one 
  produced. 
  After 
  attaining 
  a 
  lodgment 
  a 
  new 
  byssus 
  is 
  

   formed 
  and 
  attached 
  to 
  sand 
  grains 
  and 
  pebbles. 
  In 
  this 
  way 
  the 
  

   animal 
  is 
  more 
  or 
  less 
  perfectly 
  anchored, 
  and 
  partially 
  secured 
  against 
  

   dislodgment 
  by 
  waves 
  or 
  currents. 
  It 
  frequently 
  leav^es 
  the 
  burrow, 
  

   wandering 
  about 
  by 
  means 
  of 
  the 
  greatU' 
  developed 
  foot, 
  and 
  then 
  

   repeats 
  the 
  process 
  of 
  burrowing. 
  Finally 
  it 
  digs 
  into 
  the 
  soil 
  to 
  

   remain 
  permanently. 
  

  

  It 
  is 
  evident 
  that 
  the 
  conditions 
  determining 
  the 
  existence 
  of 
  the 
  

   clam 
  during 
  this 
  earl}^ 
  period 
  are 
  different 
  from 
  those 
  which 
  affect 
  

   the 
  adult. 
  The 
  distribution 
  of 
  the 
  young 
  on 
  the 
  bottom 
  and 
  the 
  sub- 
  

   sequent 
  struggle 
  to 
  effect 
  a 
  permanent 
  lodgment 
  are 
  in 
  some 
  places 
  

   peculiar. 
  It 
  may 
  be 
  well 
  to 
  consider 
  these 
  factors 
  of 
  the 
  life 
  problem 
  

   apart 
  from 
  those 
  which 
  control 
  the 
  existence 
  of 
  the 
  adult. 
  

  

  Floating 
  organisms, 
  very 
  numerous 
  in 
  kind 
  and 
  infinite 
  in 
  number, 
  

   constitute 
  the 
  food 
  of 
  a 
  vast 
  host 
  of 
  marine 
  animals. 
  Among 
  these 
  

  

  a 
  Observations 
  on 
  the 
  life-history 
  of 
  the 
  common 
  clam. 
  By 
  James 
  L. 
  Kellogg. 
  U.S. 
  Fish 
  Commis- 
  

   sion 
  Bulletin, 
  1900. 
  

  

  