﻿18 
  PROPAGATION 
  OF 
  FEESH-WATER 
  MUSSELS. 
  

  

  Glochidium 
  (pi, 
  v, 
  fig. 
  30). 
  — 
  Gravid 
  females 
  with 
  glochidia 
  are 
  

   reported 
  from 
  May 
  until 
  August. 
  In 
  1912 
  the 
  first 
  found 
  were 
  13 
  

   out 
  of 
  85 
  examined 
  on 
  June 
  17, 
  the 
  latest 
  3 
  out 
  of 
  66 
  examined 
  on 
  

   September 
  3. 
  The 
  spring 
  of 
  1912 
  was 
  late, 
  which 
  may 
  have 
  had 
  the 
  

   effect 
  of 
  delaying 
  the 
  breeding 
  season. 
  

  

  All 
  four 
  gills 
  are 
  marsupial. 
  The 
  eggs 
  are 
  pink, 
  giving 
  this 
  color 
  

   to 
  the 
  gills. 
  As 
  development 
  proceeds 
  the 
  embryos 
  lose 
  the 
  color; 
  

   but 
  if, 
  as 
  is 
  often 
  the 
  case, 
  there 
  are 
  unfertilized 
  eggs, 
  the 
  color 
  

   remains 
  until 
  the 
  eggs 
  are 
  discharged 
  with 
  the 
  glochidia. 
  

  

  Form: 
  Suborbicular; 
  the 
  outline 
  as 
  seen 
  in 
  side 
  view 
  is 
  subsemi- 
  

   circular. 
  (PI. 
  v, 
  fig. 
  30.) 
  

  

  Dimensions: 
  Height, 
  0.148 
  mm. 
  to 
  0.15 
  mm.; 
  length, 
  0.153 
  mm. 
  

   to 
  0.16 
  mm. 
  The 
  dimensions 
  of 
  this 
  shell 
  are 
  so 
  near 
  those 
  of 
  Q. 
  

   trigona 
  and 
  Q. 
  solida 
  that 
  one 
  is 
  obliged 
  to 
  rely 
  chiefly 
  on 
  the 
  form 
  to 
  

   distinguish 
  them. 
  

  

  Natural 
  infection. 
  — 
  In 
  seeking 
  the 
  natural 
  host 
  for 
  this 
  species 
  the 
  

   investigation 
  was 
  begun 
  early 
  in 
  the 
  spring; 
  although 
  infections 
  at 
  

   this 
  time 
  seemed 
  improbable, 
  it 
  was 
  necessary 
  to 
  determine 
  whether 
  

   any 
  infections 
  could 
  be 
  carried 
  over 
  winter. 
  The 
  results, 
  so 
  far 
  as 
  

   this 
  species 
  of 
  mussel 
  is 
  concerned, 
  were 
  negative; 
  but 
  a 
  common 
  

   infection 
  by 
  another 
  species 
  was 
  found 
  in 
  the 
  sturgeon, 
  Scapliorhyn- 
  

   chus 
  platorJiyncus, 
  early 
  in 
  April 
  soon 
  after 
  the 
  ice 
  broke 
  up. 
  Mate- 
  

   rial 
  was 
  obtained 
  by 
  seining 
  and 
  trammel 
  nets 
  as 
  well 
  as 
  by 
  fyke 
  or 
  

   wing 
  nets 
  and 
  fines. 
  Many 
  natural 
  infections 
  of 
  various 
  species 
  were 
  

   found 
  during 
  the 
  spring, 
  but 
  the 
  first 
  evidence 
  of 
  any 
  infection 
  

   resembling 
  the 
  glochidium 
  of 
  Q. 
  ebena 
  was 
  obtained 
  June 
  21 
  on 
  

   Micropterus 
  sahnoides. 
  This 
  was 
  a 
  single 
  glochidium; 
  similar 
  single 
  

   infections 
  were 
  found 
  in 
  June 
  on 
  Pornoxis 
  sparoides, 
  and 
  one 
  August 
  

   9 
  on 
  Pomoxis 
  sparoides, 
  and 
  four 
  the 
  same 
  date 
  on 
  Pomoxis 
  annularis.'^ 
  

  

  With 
  this 
  limited 
  evidence 
  as 
  a 
  guide, 
  experiments 
  in 
  artificial 
  

   infection 
  were 
  tried 
  upon 
  the 
  three 
  species 
  named. 
  The 
  tests, 
  

   although 
  giving 
  some 
  results 
  of 
  interest, 
  did 
  not 
  indicate 
  that 
  the 
  

   natural 
  host 
  had 
  been 
  found. 
  A 
  discussion 
  of 
  the 
  results 
  will 
  be 
  

   found 
  under 
  the 
  next 
  topic. 
  

  

  On 
  August 
  13, 
  while 
  out 
  with 
  the 
  station 
  seining 
  crew 
  engaged 
  in 
  

   mussel 
  propagation, 
  Mr. 
  T. 
  Surber 
  secured 
  a 
  specimen 
  of 
  the 
  blue 
  

   herring, 
  Pomolobus 
  clirysocMoris 
  , 
  heavily 
  infected 
  with 
  glochidia. 
  

   These, 
  upon 
  examination, 
  were 
  determined 
  to 
  be 
  Q. 
  ehena. 
  This 
  was 
  

   the 
  first 
  specimen 
  of 
  this 
  species 
  of 
  fish 
  known 
  to 
  have 
  beeii 
  taken 
  this 
  

   season 
  during 
  the 
  breeding 
  period 
  of 
  the 
  niggerhead. 
  Earlier 
  in 
  the 
  

   spring. 
  May 
  16, 
  a 
  specimen 
  was 
  brought 
  to 
  me 
  which 
  proved 
  to 
  be 
  

   heavily 
  infected, 
  but 
  not 
  with 
  the 
  niggerhead. 
  

  

  oThe 
  glochidia 
  of 
  Q. 
  ebena, 
  Q. 
  trigona, 
  and 
  Q. 
  solida, 
  as 
  will 
  be 
  seen 
  by 
  reference 
  to 
  the 
  figures, 
  do 
  not 
  differ 
  

   greatly 
  in 
  appearance. 
  This 
  makes 
  certain 
  identifications 
  difficult 
  in 
  some 
  infections. 
  (See 
  Q. 
  plicata, 
  

   under 
  natural 
  infections, 
  p. 
  27.) 
  

  

  