﻿76 
  

  

  wholly 
  to 
  the 
  sudden 
  stoppage 
  of 
  the 
  rapid 
  on-rusli 
  of 
  the 
  

   hlood 
  driven 
  from 
  the 
  heart, 
  by 
  the 
  branching 
  of 
  the 
  aorta 
  

   and 
  the 
  sudden 
  bendin? 
  upon 
  itself 
  of 
  the 
  main 
  return 
  

   branch. 
  The 
  blood 
  cannot 
  escape 
  fast 
  enough 
  into 
  the 
  

   smaller 
  vessels 
  and 
  around 
  the 
  curve, 
  and 
  so 
  is 
  piled 
  up 
  at 
  

   this 
  point,* 
  stretching 
  the 
  elastic 
  walls 
  of 
  the 
  aorta 
  into 
  quite 
  

   a 
  cavity, 
  and, 
  by 
  forming 
  a 
  sort 
  of 
  cushion 
  for 
  the 
  impulses 
  

   of 
  the 
  heart, 
  magnifies 
  the 
  beat 
  ; 
  and 
  this, 
  together 
  with 
  the 
  

   natural 
  rebound 
  of 
  elastic 
  walls 
  when 
  tightly 
  stretched 
  and 
  

   then 
  released, 
  gives 
  the 
  '^ 
  caudal 
  heart." 
  

  

  In 
  Trout 
  and 
  Salmon, 
  and 
  especially 
  in 
  Lake-Herring, 
  

   there 
  might 
  with 
  equal 
  justice 
  be 
  said 
  to 
  be 
  a 
  ''yolk 
  heart," 
  

   since 
  where 
  the 
  omphalo-meseraic 
  artery, 
  or 
  arteries, 
  pass 
  from 
  

   the 
  aorta, 
  there 
  are 
  dilatations 
  of 
  the 
  vessels, 
  and 
  the 
  same 
  

   "beating" 
  appearance 
  is 
  seen. 
  In 
  the 
  head 
  a 
  great 
  many 
  

   small 
  arteries 
  are 
  sent 
  off, 
  which 
  ramify 
  through 
  the 
  brain 
  

   and 
  surrounding 
  tissue. 
  The 
  position 
  of 
  these 
  new 
  vessels, 
  

   and 
  of 
  the 
  branchial 
  vessels^ 
  after 
  they 
  pass 
  into 
  the 
  head 
  

   tissues, 
  is 
  continually 
  changing 
  and 
  approximating 
  toward 
  

   a 
  central 
  vessel 
  on 
  the 
  ventral 
  surface 
  of 
  the 
  brain, 
  which 
  

   is 
  to 
  unite 
  with 
  the 
  body 
  aorta, 
  and 
  form 
  a 
  connection 
  

   between 
  all 
  the 
  branchial 
  vessels 
  and 
  the 
  aorta, 
  so 
  that 
  by 
  

   far 
  the 
  greater 
  portion 
  of 
  the 
  blood 
  shall 
  make 
  the 
  complete 
  

   circuit 
  of 
  the 
  body 
  before 
  returning 
  to 
  the 
  heart. 
  I 
  was 
  not 
  

   able 
  to 
  see 
  this 
  change 
  in 
  the 
  Smelt, 
  on 
  account 
  of 
  the 
  im- 
  

   possibility 
  of 
  keeping 
  the 
  young 
  fry 
  alive. 
  They 
  would 
  not 
  

   feed. 
  My 
  observations 
  upon 
  the 
  development 
  of 
  the 
  Smelt, 
  

   therefore, 
  end 
  at 
  this 
  point. 
  Much 
  of 
  the 
  embryology 
  of 
  

   this 
  paper 
  requires 
  to 
  be 
  further 
  authenticated 
  by 
  examina- 
  

   tion 
  and 
  sections. 
  This 
  work 
  I 
  hope 
  to 
  perform 
  at 
  no 
  dis- 
  

   tant 
  day. 
  

  

  * 
  Qusere. 
  Docs 
  this 
  offer 
  any 
  suggestion 
  as 
  t* 
  the 
  original 
  formation 
  of 
  a 
  

   lieart 
  ? 
  

  

  Is 
  a 
  heart 
  homologlcally 
  simply 
  an 
  improvised 
  dilatation, 
  for 
  retarded 
  bloodt 
  

   of 
  a 
  branched 
  or 
  bending 
  vessel, 
  and 
  a 
  dilatation 
  in 
  which 
  the 
  rythmical 
  pul- 
  

   sations, 
  originally 
  impressed 
  upon 
  it 
  from 
  without, 
  have 
  become 
  inherited, 
  

   and 
  are 
  now 
  originated 
  and 
  perpetuated 
  by 
  it 
  through 
  a 
  force 
  which 
  has 
  

   become 
  a 
  part 
  of 
  itself? 
  

  

  