﻿[29] 
  DEVELOPMENT 
  OF 
  OSSEOUS 
  FISHES. 
  517 
  

  

  qpment 
  of 
  the 
  skeleton 
  of 
  the 
  shoulder-girdle 
  and 
  pectoral 
  tins 
  of 
  this 
  

   type. 
  The 
  most 
  important 
  contribution 
  to 
  our 
  knowledge 
  of 
  the 
  devel- 
  

   opment 
  of 
  fishes 
  of 
  this 
  type, 
  however, 
  is 
  a 
  paper 
  by 
  Walther. 
  45 
  

  

  It 
  is 
  interesting 
  to 
  note 
  that 
  'Swirski 
  found 
  no 
  less 
  than 
  fifteen 
  carti- 
  

   laginous 
  nodules 
  at 
  the 
  distal 
  ends 
  of 
  the 
  still 
  cartilaginous 
  actinosts 
  

   or 
  basipterygial 
  pieces, 
  of 
  which 
  he 
  finds 
  four, 
  but 
  the 
  distal 
  end 
  of 
  the 
  

   fifth 
  and 
  most 
  dorsal 
  in 
  position 
  is 
  bifurcated, 
  showing 
  that 
  it 
  is 
  prob- 
  

   ably 
  compound, 
  having 
  doubtless 
  originated 
  by 
  the 
  proximal 
  coales- 
  

   cence 
  of 
  two 
  parallel 
  bars. 
  Some 
  of 
  the 
  distal 
  nodides 
  or 
  actinophores 
  

   were 
  transitory. 
  The 
  sixteen 
  or 
  seventeen 
  rays 
  of 
  the 
  pectoral 
  devel- 
  

   oped 
  as 
  do 
  those 
  of 
  the 
  rays 
  of 
  the 
  median 
  fins, 
  viz, 
  by 
  the 
  proxi- 
  

   mal 
  concrescence 
  or 
  blending 
  of 
  horn 
  fibers 
  or 
  actinotrichia. 
  The 
  large 
  

   number 
  of 
  pectoral 
  actinophores 
  found 
  at 
  various 
  stages 
  would 
  indi- 
  

   cate, 
  even 
  if 
  two 
  rays 
  must 
  be 
  reckoned 
  to 
  a 
  segment, 
  that 
  at 
  least 
  eight 
  

   metameres 
  have 
  thrust 
  processes 
  of 
  tissue 
  into 
  the 
  pectoral 
  fold 
  during 
  

   its 
  development. 
  These 
  data 
  seem 
  to 
  indicate, 
  in 
  fact, 
  that 
  considerable 
  

   reduction 
  has 
  occurred 
  in 
  the 
  number 
  of 
  metameric 
  elements 
  in 
  the 
  

   paired 
  fins 
  of 
  Teleosts, 
  since 
  certain 
  of 
  these 
  elements 
  are 
  transitory. 
  

  

  Walther's 
  paper 
  discusses 
  especially 
  the 
  chondrocranium 
  and 
  the 
  re- 
  

   lation 
  of 
  the 
  cementum 
  plates, 
  at 
  the 
  bases 
  of 
  the 
  conical 
  enamel-crowns 
  

   of 
  the 
  teeth, 
  to 
  the 
  formation 
  of 
  the 
  membrane 
  bones 
  of 
  the 
  jaws 
  and 
  

   mouth. 
  

  

  X. 
  — 
  Species 
  No. 
  1. 
  

  

  This 
  fresh 
  water 
  species, 
  which 
  I 
  cannot 
  identify, 
  has 
  a 
  very 
  adhesive 
  . 
  

   egg, 
  l.G 
  n,m 
  by 
  1 
  ,11U 
  in 
  diameter, 
  as 
  shown 
  in 
  fig. 
  31, 
  plate 
  vii. 
  The 
  blas- 
  

   toderm 
  constricts 
  the 
  yelk 
  in 
  a 
  very 
  remarkable 
  way 
  during 
  its 
  growth 
  

   over 
  the 
  yelk-globe, 
  as 
  shown 
  in 
  figs. 
  30 
  and. 
  31. 
  A 
  very 
  large 
  refrin- 
  

   gent 
  oil-drop 
  is 
  embedded 
  in 
  the 
  yelk 
  ; 
  the 
  larger 
  oil-drop 
  is 
  also 
  sur- 
  

   rounded 
  by 
  a 
  wreath 
  of 
  much 
  smaller 
  ones. 
  Kupffer's 
  vesicle 
  is 
  devel- 
  

   oped 
  under 
  the 
  tail 
  end 
  of 
  the 
  embryonic 
  axis 
  in 
  the 
  stage 
  represented 
  

   b\ 
  rig. 
  33. 
  Fig. 
  32 
  represents 
  nearly 
  the 
  same 
  stage 
  in 
  profile, 
  and 
  

   shows 
  the 
  oil-sphere 
  pushed 
  quite 
  to 
  the 
  ventral 
  and 
  anterior 
  pole 
  of 
  

   the 
  yelk, 
  where 
  it 
  remains 
  until 
  absorbed, 
  as 
  shown 
  in 
  fig. 
  34. 
  

  

  Three 
  days 
  after 
  hatching, 
  the 
  embryo 
  measures 
  about 
  4 
  ram 
  in 
  length, 
  

   has 
  a 
  well-marked 
  vitelline 
  circulation 
  developed, 
  and 
  a 
  row 
  of 
  dark 
  

   pigment 
  spots 
  are 
  developed 
  along 
  the 
  side 
  of 
  the 
  body, 
  while 
  a 
  very 
  

   singular 
  and 
  peculiar 
  arrangement 
  of 
  pigment 
  is 
  found 
  on 
  the 
  yelk- 
  

   sack. 
  On 
  the 
  latter, 
  as 
  may 
  be 
  seen 
  in 
  fig. 
  34, 
  the 
  pigment 
  spots 
  are 
  

   confined 
  to 
  the 
  noiuts 
  where 
  the 
  minute 
  vessels 
  join 
  each 
  other. 
  

  

  These 
  eggs 
  were 
  found 
  adherent 
  to 
  a 
  piece 
  of 
  leather 
  in 
  a 
  single 
  layer 
  

   at 
  Havre 
  de 
  Grace, 
  Md., 
  in 
  the 
  early 
  part 
  of 
  May, 
  1881. 
  The 
  adhesive 
  

  

  «"' 
  Johannes 
  Walther. 
  Die 
  Entwickelung 
  der 
  Deckknochen 
  am 
  Kopfskelett 
  des 
  

   Hechtes 
  (Esox 
  lueius). 
  Jenaische 
  Zeitschr., 
  xvi, 
  n. 
  f., 
  ix, 
  1. 
  nnd 
  2. 
  Heft, 
  Jena, 
  1882, 
  

   pp. 
  59-87, 
  pis. 
  iii-iv. 
  

  

  