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  PROPAGATION 
  OF 
  FRESH-WATER 
  MUSSELS. 
  

  

  whether 
  infection 
  takes 
  place 
  in 
  the 
  autumn 
  or 
  spring. 
  Lilhe 
  (1895) 
  

   intimates 
  that 
  there 
  is 
  some 
  development 
  of 
  the 
  larvae 
  during 
  the 
  

   winter 
  in 
  the 
  case 
  of 
  the 
  long-period 
  breeder 
  Anodonta 
  cataracta. 
  

  

  Lefevre 
  and 
  Curtis 
  (1912) 
  assume 
  that 
  development 
  for 
  anodontas 
  

   is 
  (complete 
  in 
  the 
  autumn. 
  Harms 
  (1909) 
  suggests 
  the 
  probability 
  

   of 
  two 
  broods 
  in 
  the 
  short-period 
  breeder, 
  M. 
  margaritifera, 
  during 
  

   July 
  and 
  August. 
  Conner 
  (1909, 
  p. 
  112) 
  gives 
  the 
  breeding 
  period 
  

   for 
  this 
  species 
  as 
  June 
  and 
  August. 
  I 
  have 
  seen 
  indications 
  of 
  two 
  

   broods 
  m 
  the 
  breeding 
  of 
  Q. 
  ebena, 
  and 
  Lefevre 
  and 
  Curtis 
  (1912, 
  p. 
  

   114) 
  mention 
  similar 
  observations. 
  Ihe 
  settlement 
  of 
  this 
  question 
  

   would 
  require 
  the 
  keeping 
  of 
  females 
  under 
  observation 
  during 
  the 
  

   breeding 
  period, 
  but 
  there 
  is 
  the 
  difficulty 
  that 
  no 
  one, 
  so 
  far 
  as 
  I 
  

   know, 
  has 
  yet 
  succeeded 
  in 
  getting 
  these 
  mussels 
  to 
  breed 
  in 
  cap- 
  

   tivity. 
  

  

  I 
  have 
  reported 
  the 
  absence 
  of 
  infections 
  by 
  Q. 
  pushdosa 
  after 
  

   September 
  1. 
  It 
  is 
  probable 
  that 
  September 
  marks 
  the 
  limit 
  of 
  

   infections 
  by 
  short-period 
  breeders. 
  The 
  findmg 
  of 
  mfections 
  by 
  

   long-period 
  breeders 
  early 
  in 
  the 
  autumn 
  and 
  spring 
  upon 
  the 
  stur- 
  

   geon, 
  Scaphorhynclius 
  platorhyncJms, 
  and 
  the 
  wintering 
  of 
  Q. 
  Jieros 
  

   upon 
  its 
  host 
  show 
  that 
  mfections 
  are 
  not 
  confined 
  to 
  late 
  spring. 
  It 
  

   is 
  to 
  be 
  expected 
  that 
  the 
  period 
  of 
  uifection 
  would 
  be 
  adapted 
  in 
  

   large 
  measure 
  to 
  the 
  habits 
  and 
  seasonal 
  migrations 
  of 
  fishes. 
  

  

  In 
  general 
  we 
  may 
  say 
  that 
  for 
  most 
  mussels 
  in 
  this 
  climate 
  the 
  

   sea: 
  an 
  of 
  infection 
  comes 
  in 
  the 
  warmer 
  months. 
  In 
  southern 
  waters 
  

   as 
  much 
  restriction 
  would 
  not 
  be 
  expected. 
  

  

  Metamorphosis 
  during 
  the 
  parasitic 
  stage. 
  — 
  The 
  development 
  of 
  the 
  

   young 
  mussels 
  in 
  the 
  post-embryonic 
  or 
  parasitic 
  period 
  has 
  been 
  

   systematically 
  worked 
  out 
  in 
  a 
  number 
  of 
  forms 
  (Brown, 
  1878a, 
  1878b, 
  

   1884, 
  1889; 
  'Schierholz, 
  1888; 
  Harms, 
  1907a, 
  1907b, 
  1907c, 
  1908, 
  

   1909; 
  Lefevre 
  and 
  Curtis, 
  1912). 
  I 
  wish 
  here 
  to 
  caU 
  attention 
  to 
  

   some 
  apparently 
  decided 
  differences 
  in 
  extent 
  of 
  development 
  

   observed 
  in 
  natural 
  infections. 
  DifTerences 
  in 
  the 
  amount 
  of 
  devel- 
  

   opment 
  of 
  the 
  larvae 
  at 
  the 
  end 
  of 
  the 
  period 
  of 
  parasitism 
  are 
  very 
  

   strikingly 
  shown 
  in 
  a 
  comparison 
  of 
  such 
  species 
  as 
  Lampsilis 
  liga- 
  

   mentina 
  and 
  Lampsilis 
  Isevissima 
  (Coker 
  and 
  Surber, 
  1911). 
  In 
  the 
  

   case 
  of 
  the 
  former 
  the 
  juvenile 
  mussel 
  leaves 
  its 
  host 
  with 
  no 
  sheU 
  

   beyond 
  that 
  of 
  the 
  glochidium 
  (Lefevre 
  and 
  Curtis, 
  1912); 
  in 
  the 
  

   latter 
  there 
  is 
  a 
  relatively 
  enormous 
  growth. 
  This 
  extra-glochidial 
  

   growth 
  I 
  have 
  observed 
  in 
  the 
  following: 
  Lampsilis 
  Ixvissima, 
  L. 
  

   alata, 
  L. 
  gracilis, 
  Plagiola 
  donaciformis 
  , 
  P. 
  elegans 
  (Howard, 
  1912), 
  

   and 
  Quadrula 
  pustulosa. 
  The 
  growth 
  in 
  the 
  case 
  of 
  the 
  large 
  glochidia 
  

   of 
  L. 
  alata 
  (pi. 
  iv, 
  fig. 
  28) 
  and 
  Q. 
  pustulosa 
  (pi. 
  in, 
  fig. 
  19) 
  is 
  only 
  

   sufficient 
  to 
  give 
  the 
  form 
  of 
  the 
  shell 
  of 
  the 
  adult 
  mussel 
  to 
  the 
  

   juvenile. 
  In 
  the 
  others, 
  which 
  have 
  very 
  small 
  glochidia, 
  the 
  great 
  

   growth 
  dm*ing 
  the 
  parasitic 
  period 
  would 
  seem 
  to 
  be 
  a 
  compensatory 
  

  

  