﻿[21] 
  DEVELOPMENT 
  OF 
  OSSEOUS 
  FISHES. 
  509 
  

  

  the 
  sides 
  of 
  the 
  body. 
  The 
  memoir 
  of 
  de 
  Quatrefages 
  38 
  is, 
  however, 
  

   very 
  superficial, 
  for 
  the 
  courses 
  and 
  distribution 
  of 
  the 
  blood-vessels 
  in 
  

   the 
  embryo 
  are 
  drawn 
  altogether 
  diagranimatically 
  and 
  with 
  the 
  help 
  

   of 
  the 
  imagination 
  of 
  the 
  artist. 
  The 
  next 
  paper 
  39 
  published 
  was 
  by 
  the 
  

   writer, 
  in 
  which 
  some 
  of 
  the 
  stages 
  of 
  development 
  of 
  Siphostomafuscum 
  

   were 
  discussed 
  and 
  described. 
  About 
  two 
  years 
  later 
  Dr. 
  J. 
  P. 
  McMur- 
  

   rich 
  took 
  up 
  the 
  study 
  of 
  the 
  development 
  of 
  this 
  species 
  and 
  published 
  

   a 
  memoir 
  40 
  which 
  is 
  valuable 
  for 
  the 
  information 
  it 
  affords 
  as 
  to 
  the 
  

   ontogeny 
  of 
  the 
  cranial 
  skeleton. 
  

  

  The 
  eggs 
  of 
  Siphostoma 
  are 
  developed 
  under 
  a 
  pair 
  of 
  integumentary 
  

   folds 
  placed 
  behind 
  the 
  vent, 
  forming 
  a 
  brood-pouch, 
  which 
  is 
  devel- 
  

   oped 
  on 
  the 
  under 
  side 
  of 
  the 
  tail 
  of 
  the 
  female. 
  The 
  ova 
  are 
  small, 
  

   measuring 
  only 
  about 
  0.75 
  mm 
  in 
  diameter. 
  They 
  are 
  embedded 
  in 
  a 
  

   viscid 
  mucus 
  contained 
  within 
  the 
  pouch 
  alluded 
  to. 
  A 
  blastodisk 
  is 
  

   evidently 
  formed 
  in 
  the 
  usual 
  way. 
  The 
  yelk 
  is 
  clear 
  lemon-yellow 
  in 
  

   color, 
  and 
  its 
  outer 
  stratum 
  contains 
  small, 
  numerous 
  deeper 
  yellow 
  

   oil 
  drops, 
  the 
  distribution 
  of 
  which 
  is 
  shown 
  in 
  fig. 
  20, 
  plate 
  iv. 
  The 
  

   presence 
  of 
  Kupffer's 
  vesicle 
  was 
  not 
  made 
  out 
  at 
  this 
  stage. 
  

  

  The 
  next 
  stage 
  of 
  development, 
  which 
  was 
  observed 
  in 
  the 
  eggs 
  taken 
  

   from 
  the 
  brood-pouch 
  of 
  another 
  male, 
  is 
  represented 
  in 
  fig. 
  19, 
  when 
  the 
  

   embryo, 
  after 
  being 
  freed 
  from 
  the 
  egg, 
  measured 
  very 
  nearly 
  3 
  mra 
  in 
  

   length. 
  This 
  is 
  a 
  considerably 
  earlier 
  stage 
  than 
  that 
  represented 
  by 
  

   fig. 
  1, 
  pi. 
  xlii, 
  in 
  McMurrich's 
  paper, 
  as 
  the 
  fold 
  indicating 
  the 
  commence- 
  

   ment 
  of 
  the 
  formation 
  of 
  the 
  caudal 
  fin 
  is 
  not 
  yet 
  present 
  in 
  fig. 
  19. 
  The 
  

   median 
  aorta 
  and 
  caudal 
  artery 
  extend 
  almost 
  to 
  the 
  end 
  of 
  the 
  tail, 
  

   where 
  it 
  is 
  continued 
  into 
  the 
  recurrent 
  cava 
  and 
  the 
  subintestinal 
  vein 
  

   which 
  return 
  the 
  blood 
  to 
  the 
  heart. 
  As 
  soon 
  as 
  the 
  subintestinal 
  vein 
  

   reaches 
  the 
  posterior 
  pole 
  of 
  the 
  yelk 
  it 
  bends 
  down 
  and 
  traverses 
  its 
  

   posterior 
  median 
  and 
  anterior 
  face 
  towards 
  the 
  heart, 
  the 
  venous 
  end 
  of 
  

   which 
  rests 
  upon 
  the 
  yelk. 
  The 
  branchial 
  arches 
  are 
  formed, 
  though 
  

   there 
  are 
  no 
  branchial 
  filaments 
  yet 
  developed. 
  The 
  pectoral 
  fin-fold 
  is 
  

   already 
  present 
  as 
  a 
  low 
  lobular 
  process 
  just 
  behind 
  the 
  auditory 
  capsule. 
  

   The 
  dorsal 
  fin 
  is 
  just 
  becoming 
  clearly 
  evident 
  as 
  a 
  low 
  median 
  fold 
  be- 
  

   hind 
  the 
  vent. 
  There 
  is 
  as 
  yet 
  no 
  trace 
  of 
  an 
  anal 
  fin 
  fold 
  visible. 
  The 
  

   oil 
  drops 
  have 
  a 
  more 
  general 
  distribution 
  over 
  the 
  yelk 
  than 
  in 
  flu. 
  20; 
  

   the 
  head 
  is 
  much 
  flexed 
  downward, 
  and 
  the 
  brain 
  is 
  very 
  conspicuous, 
  

   in 
  passing 
  I 
  w 
  r 
  ould 
  state 
  that 
  in 
  McMurrich's 
  fig. 
  1 
  the 
  mid-brain 
  is 
  

   identified 
  by 
  mistake 
  with 
  the 
  cerebellum, 
  the 
  cerebellum 
  is 
  confounded 
  

   with 
  the 
  pineal 
  gland, 
  while 
  the 
  medulla 
  oblongata 
  is 
  erroneously 
  iden- 
  

   tified 
  with 
  the 
  mid-brain 
  and 
  medulla 
  oblongata 
  together. 
  

  

  3t, 
  A. 
  de 
  Quatrefages. 
  Memoire 
  sur 
  les 
  embryons 
  des 
  Syngnathes 
  (Syngnathus 
  

   ophidion, 
  Linn.), 
  Ann. 
  des 
  Sci. 
  Naturelles, 
  xviii, 
  2d 
  ser., 
  1842, 
  pp. 
  193-212, 
  pis. 
  2. 
  

  

  39 
  Ryder. 
  A 
  contribution 
  to 
  the 
  development 
  and 
  morphology 
  of 
  the 
  Lophobranchi- 
  

   ates; 
  (Hippocampus 
  antiquorum, 
  the 
  sea-horse). 
  Bull. 
  U. 
  S. 
  Fish 
  Commission, 
  i, 
  

   1881, 
  pp. 
  191-199, 
  pi. 
  xvii. 
  

  

  40 
  J. 
  P. 
  McMurrich. 
  On 
  the 
  osteology 
  and 
  development 
  of 
  Syngnathus 
  peckianus 
  

   (Storer), 
  Quar. 
  Jour. 
  Mio. 
  Sci., 
  xxiii, 
  n. 
  s., 
  pp. 
  623-650, 
  pie. 
  2. 
  

  

  