﻿PBOPAGATION 
  OF 
  FRESH-WATER 
  MUSSELS. 
  39 
  

  

  parasitic 
  stage), 
  the 
  host 
  must 
  furnish 
  the 
  material. 
  In 
  these 
  cases 
  I 
  

   have 
  observed 
  ocular 
  evidence 
  of 
  absorptive 
  processes 
  whose 
  exact 
  

   nature 
  I 
  hope 
  to 
  investigate 
  later. 
  

  

  ^Frequency 
  of 
  infections. 
  — 
  To 
  know 
  the 
  proportion 
  of 
  infected 
  fish 
  

   in 
  nature 
  is 
  a 
  matter 
  of 
  considerable 
  importance. 
  The 
  expectation 
  

   would 
  be 
  that 
  it 
  must, 
  from 
  the 
  nature 
  of 
  the 
  case, 
  vary 
  according 
  to 
  

   species, 
  locality, 
  season, 
  abundance 
  of 
  mussels, 
  source 
  of 
  the 
  fish, 
  and 
  

   the 
  hke. 
  The 
  results 
  I 
  have 
  given 
  for 
  the 
  channel 
  cat, 
  Ictalurus 
  

   punctatus, 
  give 
  an 
  idea 
  of 
  the 
  variation 
  that 
  occurs. 
  We 
  see 
  that 
  for 
  

   this 
  fish 
  during 
  the 
  months 
  of 
  July 
  and 
  August, 
  the 
  breeding 
  season 
  

   for 
  the 
  warty-back 
  Q. 
  pustulosa, 
  there 
  were 
  17 
  infected 
  fish 
  out 
  of 
  39 
  

   examined. 
  The 
  entire 
  absence 
  of 
  infections 
  in 
  Septen^ber 
  from 
  an 
  

   examination 
  of 
  98 
  fish 
  is 
  explained 
  by 
  the 
  season, 
  which 
  was 
  after 
  

   the 
  close 
  of 
  the 
  breeding 
  period 
  for 
  the 
  mussel. 
  The 
  figures 
  given 
  by 
  

   Surber 
  (1913) 
  of 
  no 
  infections 
  out 
  of 
  21 
  fish 
  of 
  this 
  species 
  examined 
  

   in 
  August, 
  I 
  can 
  hardly 
  explain 
  unless 
  it 
  is 
  that 
  the 
  fish 
  were 
  not 
  

   taken 
  near 
  mussel 
  beds, 
  or 
  that 
  owing 
  to 
  the 
  position 
  of 
  the 
  glochidia 
  

   they 
  might 
  be 
  easily 
  overlooked 
  in 
  hving 
  fish. 
  

  

  The 
  drum 
  or 
  sheepshead, 
  Aplodinotus 
  grunniens, 
  on 
  account 
  of 
  the 
  

   fact 
  that 
  it 
  is 
  the 
  host 
  for 
  a 
  large 
  number 
  of 
  species, 
  runs 
  the 
  chance 
  

   of 
  more 
  frequent 
  infections. 
  

  

  In 
  a 
  region 
  where 
  artificial 
  infection 
  has 
  been 
  carried 
  on 
  upon 
  a 
  

   large 
  scale, 
  it 
  would 
  be 
  difficult 
  to 
  determine 
  satisfactorily 
  anything 
  

   of 
  this 
  nature 
  regarding 
  the 
  species 
  employed 
  in 
  the 
  operations; 
  this 
  

   difficulty 
  has 
  arisen 
  in 
  investigations 
  at 
  the 
  Fairport 
  biological 
  labor- 
  

   atory, 
  fish 
  having 
  several 
  times 
  been 
  captured 
  which 
  had 
  been 
  without 
  

   doubt 
  artificially 
  infected. 
  

  

  Extent 
  of 
  individual 
  infections. 
  — 
  Certain 
  species 
  of 
  fish 
  commonly 
  

   in 
  nature 
  carry 
  a 
  remarkably 
  large 
  number 
  of 
  glochidia; 
  for 
  example, 
  

   the 
  drum, 
  Aplodinotus 
  grunniens, 
  and 
  the 
  herring, 
  Pomolohus 
  chryso- 
  

   chloris, 
  have 
  been 
  found 
  with 
  thousands; 
  but 
  a 
  small 
  number 
  seems 
  

   more 
  common. 
  Heavy 
  infections 
  are 
  difficult 
  to 
  explain, 
  except 
  

   upon 
  the 
  supposition 
  that 
  they 
  take 
  place 
  at 
  the 
  time 
  of 
  extrusion 
  

   from 
  the 
  mussel, 
  or 
  as 
  the 
  result 
  of 
  oft-repeated 
  infections. 
  This 
  

   brings 
  up 
  the 
  subject 
  of 
  the 
  following 
  topic. 
  

  

  Conditions 
  of 
  infection 
  in 
  nature. 
  — 
  I 
  know 
  of 
  no 
  observations 
  of 
  the 
  

   infection 
  of 
  fish 
  in 
  nature. 
  Latter 
  (1891) 
  found 
  that 
  he 
  could 
  pro- 
  

   duce 
  a 
  discharge 
  of 
  glochidia 
  by 
  gently 
  striking 
  the 
  water 
  in 
  which 
  

   anodons 
  were 
  l5n.ng 
  and 
  made 
  further 
  observations 
  upon 
  the 
  emission 
  

   of 
  glochidia 
  which, 
  he 
  seems 
  to 
  conclude, 
  argue 
  against 
  the 
  necessity 
  

   of 
  the 
  presence 
  of 
  fish. 
  I 
  believe, 
  however, 
  they 
  support 
  the 
  prob- 
  

   ability 
  that 
  the 
  approach 
  of 
  fish 
  is 
  the 
  normal 
  stimulus 
  in 
  ehciting 
  

   the 
  emission 
  of 
  glochidia. 
  The 
  cases 
  of 
  heavy 
  individual 
  infection 
  

   of 
  fish 
  found 
  in 
  the 
  species 
  mentioned 
  above 
  suggest 
  that 
  the 
  glochidia 
  

   must 
  be 
  extruded 
  when 
  the 
  fish 
  are 
  in 
  close 
  proximity, 
  otherwise 
  the 
  

  

  