﻿PROPAGATION 
  OF 
  FRESH-WATER 
  MUSSELS. 
  45 
  

  

  probably 
  completed 
  in 
  the 
  fall. 
  The 
  time 
  of 
  discharge 
  of 
  the 
  young 
  

   mussels 
  is 
  yet 
  to 
  be 
  determined, 
  but 
  the 
  appearance 
  of 
  glochidia 
  again 
  

   in 
  early 
  spring 
  would 
  seem 
  to 
  indicate 
  that 
  the 
  juveniles 
  escape 
  in 
  the 
  

   fal! 
  or 
  early 
  winter. 
  

  

  Among 
  the 
  six 
  lots 
  of 
  marsupial 
  juveniles 
  that 
  I 
  collected, 
  the 
  

   degree 
  of 
  development 
  varied 
  slightly 
  as 
  to 
  amount 
  of 
  shell 
  growth, 
  

   otherwise 
  there 
  seemed 
  to 
  be 
  little 
  difference. 
  This 
  growth 
  consists 
  

   of 
  a 
  narrow 
  rim 
  only 
  around 
  the 
  edge 
  of 
  the 
  glochidia! 
  shell. 
  The 
  

   hooks 
  of 
  the 
  glochidium 
  are 
  still 
  much 
  in 
  evidence 
  but 
  are 
  much 
  

   weaker 
  than 
  in 
  parasitic 
  forms. 
  A 
  noticeable 
  feature 
  is 
  the 
  large 
  

   proportion 
  of 
  gaping 
  shells 
  as 
  compared 
  with 
  a 
  similar 
  lot 
  of 
  glochidia. 
  

   It 
  would 
  seem 
  that 
  with 
  the 
  loss 
  of 
  the 
  powerful 
  single 
  adductor 
  

   muscle 
  the 
  action 
  of 
  closing 
  is 
  less 
  vigorous. 
  Between 
  the 
  gaping 
  

   valves 
  can 
  be 
  seen 
  the 
  ciliated 
  foot, 
  on 
  each 
  side 
  the 
  gill 
  papillae, 
  two 
  

   adductor 
  muscles, 
  mantle, 
  etc., 
  indicating 
  a 
  development 
  equal 
  to 
  

   that 
  of 
  other 
  young 
  Naiades 
  at 
  the 
  end 
  of 
  parasitism. 
  

  

  I 
  have 
  tested 
  the 
  reaction 
  of 
  the 
  glochidia 
  in 
  the 
  presence 
  of 
  fish 
  

   and 
  obtained 
  strong 
  evidence 
  that 
  they 
  do 
  not 
  respond 
  as 
  other 
  

   known 
  parasitic 
  forms. 
  Mature 
  glochidia 
  taken 
  in 
  March 
  were 
  

   employed. 
  In 
  an 
  exposure 
  to 
  fish 
  for 
  an 
  hour 
  they 
  •'"ailed 
  to 
  give 
  the 
  

   usual 
  infection. 
  A 
  few 
  glochidia 
  lodged 
  in 
  the 
  mouths 
  of 
  the 
  fish, 
  but 
  

   no 
  encystment 
  could 
  be 
  detected. 
  The 
  fish 
  showed 
  no 
  response. 
  

   Following 
  this 
  tost 
  the 
  fish 
  were 
  exposed 
  for 
  10 
  minutes 
  to 
  the 
  

   glochidia 
  of 
  Si/mijliynota 
  complanata 
  (Barnes.) 
  These 
  rapidly 
  became 
  

   attached 
  and 
  the 
  fish 
  showed 
  considerable 
  uneasiness, 
  in 
  marked 
  

   contrast 
  to 
  their 
  indifference 
  in 
  the 
  presence 
  of 
  the 
  other 
  glochidia." 
  

  

  From 
  these 
  observations 
  I 
  think 
  I 
  am 
  warranted 
  in 
  concmding 
  that 
  

   this 
  mussel 
  passes 
  through 
  its 
  metamorphosis 
  without 
  parasitism. 
  

   The 
  absence 
  of 
  a 
  conglutinate 
  (Lefevre 
  and 
  Curtis, 
  1912) 
  or 
  placenta 
  

   (Sterki, 
  1898) 
  is 
  of 
  interest, 
  as 
  we 
  have 
  here 
  a 
  case 
  of 
  nonparasitic 
  

   development 
  independent 
  of 
  this 
  type 
  of 
  structure 
  found 
  in 
  Strophitus. 
  

  

  It 
  is 
  a 
  question 
  whether 
  the 
  development, 
  following 
  the 
  escape 
  of 
  

   the 
  glochidium 
  from 
  the 
  egg, 
  is 
  aided 
  by 
  absorption 
  of 
  food 
  or 
  not. 
  

   One 
  would 
  expect 
  the 
  former, 
  as 
  it 
  is 
  evident 
  that 
  this 
  species 
  has 
  

   descended 
  from 
  parasitic 
  ancestors 
  which 
  received 
  extraneous 
  

   nutrition 
  during 
  the 
  parasitic 
  period. 
  

  

  The 
  discovery 
  of 
  the 
  absence 
  of 
  parasitism 
  in 
  this 
  species 
  already 
  

   possessing 
  the 
  distinction 
  of 
  being 
  hermaphroditic 
  certainly 
  adds 
  to 
  

   its 
  reputation 
  as 
  an 
  eccentric 
  among 
  its 
  relatives 
  in 
  the 
  Unionidse. 
  

  

  a 
  Observations 
  made 
  since 
  the 
  above 
  was 
  written 
  indicate 
  that 
  juveniles 
  may 
  be 
  found 
  in 
  the 
  marsupium 
  

   at 
  almost 
  any 
  time 
  during 
  the 
  year. 
  I 
  have 
  also 
  been 
  able 
  to 
  secure 
  infections 
  and 
  encystment 
  on 
  fishes 
  

   with 
  Anodonta 
  imbeciUis 
  as 
  well 
  as 
  Strophitus 
  edentulus. 
  In 
  the 
  latter 
  complete 
  metamorphosis 
  was 
  

   observed. 
  Thus 
  for 
  edentulus 
  we 
  have 
  indicated 
  facultative 
  parasitism, 
  while 
  in 
  the 
  other 
  we 
  have 
  a 
  

   persistence 
  of 
  the 
  parasitic 
  reaction 
  at 
  least 
  when 
  artificially 
  brought 
  in 
  contact 
  with 
  a 
  liost. 
  Meta- 
  

   morphosis 
  on 
  fishes 
  was 
  not 
  secured 
  in 
  A. 
  imbeciUis. 
  Abundant 
  additional 
  evidence 
  is 
  at 
  hand 
  that 
  

   development 
  in 
  this 
  (imbeciUis) 
  species 
  normally 
  proceeds 
  without 
  parasitism. 
  

  

  