﻿[47] 
  DEVELOPMENT 
  OF 
  OSSEOUS 
  FISHES. 
  535 
  

  

  found 
  in 
  a 
  submerged 
  pile 
  of 
  shot 
  or 
  other 
  spherical 
  bodies 
  which 
  had 
  

   been 
  piled 
  in 
  a 
  heap. 
  It 
  was 
  evident 
  that 
  the 
  male 
  was 
  forcing 
  fresh 
  

   water 
  through 
  the 
  interstices 
  in 
  this 
  mass 
  of 
  eggs 
  by 
  hovering 
  over 
  it 
  

   and 
  vibrating 
  the 
  anal, 
  ventral, 
  and 
  pectoral 
  fins 
  rapidly. 
  

  

  All 
  of 
  the 
  ova 
  left 
  in 
  the 
  care 
  of 
  the 
  male 
  hatched, 
  while 
  about 
  one- 
  

   half 
  of 
  the 
  mass 
  which 
  he 
  had 
  detached 
  from 
  the 
  bottom 
  of 
  the 
  aqua- 
  

   rium 
  on 
  the 
  third 
  day, 
  during 
  some 
  of 
  his 
  vigorous 
  efforts 
  at 
  changing 
  

   the 
  water, 
  were 
  transferred 
  to 
  another 
  aquarium, 
  supplied 
  with 
  run- 
  

   ning 
  water, 
  and 
  left 
  to 
  themselves. 
  Those 
  which 
  were 
  hatched 
  by 
  the 
  

   artificial 
  means 
  just 
  described 
  did 
  not 
  come 
  out 
  as 
  well 
  as 
  those 
  left 
  to 
  

   hatch 
  under 
  natural 
  conditions. 
  Nearly 
  one-half 
  of 
  the 
  former 
  failed 
  

   to 
  hatch, 
  apparently 
  because 
  they 
  were 
  not 
  agitated 
  so 
  as 
  to 
  force 
  fresh 
  

   water 
  through 
  them 
  and 
  kept 
  clean 
  by 
  the 
  assiduous 
  attentions 
  of 
  the 
  

   male 
  parent. 
  

  

  The 
  eggs 
  measure 
  about 
  one-sixth 
  of 
  an 
  inch 
  after 
  the 
  large 
  water 
  

   space 
  is 
  formed, 
  which 
  is 
  normally 
  developed 
  in 
  this, 
  as 
  in 
  the 
  ova 
  of 
  

   other 
  fishes, 
  after 
  fertilization, 
  the 
  zona 
  radiata 
  being 
  lifted 
  up 
  some- 
  

   what 
  from 
  the 
  vitellus. 
  The 
  vitellus 
  measures 
  one-eighth 
  of 
  an 
  inch 
  in 
  

   diameter. 
  The 
  egg-membrane 
  is 
  double, 
  that 
  is, 
  there 
  is 
  a 
  thin 
  inner 
  

   membrane 
  representing 
  the 
  zona 
  radiata, 
  external 
  to 
  the 
  latter 
  and 
  

   supported 
  on 
  columnar 
  processes 
  of 
  itself 
  which 
  rest 
  upon 
  the 
  inner 
  

   membrane 
  ; 
  there 
  is 
  a 
  second 
  one 
  composed 
  entirely 
  of 
  a 
  highly 
  elastic 
  

   adhesive 
  substance. 
  The 
  columns 
  supporting 
  the 
  outer 
  elastic 
  layer 
  

   rest 
  on 
  the 
  zona 
  and 
  cause 
  the 
  outer 
  layer 
  to 
  be 
  separated 
  very 
  dis- 
  

   tinctly 
  from 
  the 
  inner 
  one. 
  It 
  is 
  these 
  elastic 
  columns 
  and 
  the 
  elastic 
  

   outer 
  adhesive 
  membrane 
  which 
  permits 
  the 
  adult 
  fish 
  to 
  shake 
  and 
  

   move 
  the 
  mass 
  of 
  ova 
  so 
  violently 
  without 
  injury 
  to 
  the 
  embryos 
  in 
  

   process 
  of 
  development 
  within. 
  This 
  peculiar 
  double 
  egg-membrane, 
  

   with 
  a 
  well 
  defined 
  space 
  between 
  its 
  inner 
  and 
  outer 
  layers, 
  is 
  highly 
  

   characteristic, 
  and 
  bears 
  no 
  resemblance 
  to 
  the 
  thick, 
  simple 
  zona 
  in- 
  

   vesting 
  the 
  egg 
  of 
  JElurichthys, 
  nor 
  has 
  anything 
  resembling 
  it 
  ever 
  

   been 
  described, 
  as 
  far 
  as 
  I 
  am 
  aware, 
  in 
  the 
  ova 
  of 
  any 
  other 
  Teleos- 
  

   tean. 
  

  

  The 
  germinal 
  disk 
  was 
  formed 
  at 
  the 
  upper 
  pole 
  of 
  the 
  vitellus 
  im- 
  

   mediately 
  after 
  oviposition 
  and 
  gradually 
  spread 
  in 
  the 
  usual 
  manner 
  

   over 
  the 
  lower 
  pole 
  of 
  the 
  opaque, 
  whitish, 
  granular, 
  vitelline 
  globe. 
  

   In 
  the 
  early 
  part 
  of 
  the 
  second 
  day 
  the 
  body 
  of 
  the 
  young 
  fish 
  was 
  dis- 
  

   tinctly 
  outlined 
  and 
  the 
  tail 
  had 
  grown 
  out 
  to 
  a 
  considerable 
  length, 
  

   and 
  before 
  the 
  body 
  of 
  the 
  embryo 
  had 
  encircled 
  much 
  more 
  than 
  one- 
  

   fourth 
  of 
  the 
  circumference 
  of 
  the 
  vitellus, 
  as 
  shown 
  in 
  figs. 
  154 
  and 
  

   155 
  — 
  the 
  first 
  figure 
  being 
  drawn 
  from 
  a 
  hardened 
  embryo 
  of 
  the 
  

   second 
  day, 
  viewed 
  as 
  an 
  opaque 
  object 
  and 
  the 
  second 
  from 
  a 
  living 
  

   embryo 
  of 
  the 
  same 
  age, 
  viewed 
  as 
  a 
  transparent 
  object. 
  On 
  the 
  third 
  

   day, 
  the 
  tail 
  of 
  the 
  embryo 
  had 
  acquired 
  considerable 
  length, 
  as 
  shown 
  

   in 
  fig. 
  159, 
  and 
  its 
  free 
  extremity 
  was 
  moved 
  from 
  side 
  to 
  side 
  grace- 
  

  

  