﻿386 
  JOHN 
  RENNIB. 
  

  

  extended 
  type, 
  stretching 
  tlie 
  whole 
  length 
  of 
  the 
  intestine 
  in 
  

   two 
  narrow 
  bands, 
  a 
  condition 
  which 
  is 
  common 
  in 
  small 
  

   slender 
  bodied 
  fishes. 
  A 
  principal 
  islet 
  was 
  not 
  found 
  by 
  

   dissection, 
  but 
  on 
  sectioning 
  the 
  entire 
  viscera 
  in 
  the 
  usual 
  

   region 
  of 
  its 
  occurrence 
  several 
  fairly 
  large 
  islets 
  of 
  irregular 
  

   outline 
  were 
  found 
  (fig. 
  6). 
  

  

  H 
  ip 
  pogloss 
  us 
  vulgar 
  is, 
  Pleuronectesplatessa, 
  etc. 
  

   — 
  In 
  the 
  Pleuronectidse 
  examined 
  the 
  position 
  of 
  the 
  principal 
  

   islet 
  is 
  the 
  same, 
  and 
  they 
  may 
  therefore 
  in 
  this 
  section 
  be 
  

   referred 
  to 
  collectively. 
  It 
  is 
  the 
  same 
  as 
  in 
  Zeus, 
  viz. 
  

   within 
  a 
  small 
  pancreatic 
  mass 
  attached 
  to 
  the 
  gall-bladder. 
  

   In 
  the 
  larger 
  forms, 
  e. 
  g. 
  Hippoglossus, 
  it 
  is 
  very 
  apparent 
  

   as 
  an 
  ovoid 
  mass 
  of 
  a 
  ruddy 
  colour. 
  Here 
  the 
  pancreatic 
  

   investment 
  is 
  slight. 
  In 
  smaller 
  forms 
  the 
  outline 
  of 
  the 
  

   islet 
  is 
  not 
  so 
  apparent, 
  being 
  masked 
  by 
  the 
  surrounding 
  

   zymogenous 
  tissue. 
  Smaller 
  islets 
  exist 
  in 
  other 
  parts 
  of 
  the 
  

   pancreas; 
  thus 
  in 
  both 
  Hippoglossus 
  and 
  in 
  Pleuronectes 
  

   a 
  fairly 
  large 
  one 
  occurs 
  with 
  very 
  great 
  frequency, 
  if 
  not 
  

   with 
  absolute 
  regularity, 
  near 
  the 
  origin 
  of 
  the 
  pyloric 
  casca. 
  

  

  Syngnathus 
  acus, 
  Nerophis 
  asquoreus, 
  Syphonos- 
  

   toma 
  typhle. 
  — 
  In 
  these 
  Lophobranchs 
  the 
  pancreas 
  consists 
  

   mainly 
  of 
  two 
  well-defined 
  bands 
  following 
  the 
  blood-vessels 
  

   alongside 
  the 
  gut. 
  On 
  one 
  of 
  these 
  portions 
  where 
  the 
  

   portal 
  vein 
  crosses 
  to 
  the 
  liver 
  (the 
  usual 
  position, 
  in 
  fact) 
  

   the 
  principal 
  islet 
  occurs 
  as 
  a 
  small, 
  somewhat 
  flattened, 
  ovoid 
  

   body, 
  whitish 
  in 
  colour, 
  slightly 
  pigmented, 
  and 
  about 
  1 
  mm. 
  

   in 
  length 
  in 
  adult 
  specimens. 
  Its 
  position 
  in 
  the 
  three 
  

   species 
  is 
  identical; 
  it 
  is 
  found 
  most 
  readily 
  by 
  dissection 
  

   from 
  the 
  right 
  side, 
  lying 
  between 
  the 
  mesenteric 
  artery 
  and 
  

   the 
  portal 
  vein 
  (fig. 
  3). 
  

  

  In 
  my 
  previous 
  paper 
  I 
  enumerated 
  certain 
  species 
  in 
  which 
  

   a 
  principal 
  islet 
  existed, 
  and 
  in 
  the 
  foregoing 
  statement 
  such 
  

   particulars 
  of 
  its 
  position 
  in 
  the 
  several 
  instances 
  are 
  given 
  

   as 
  will 
  enable 
  its 
  occurrence 
  to 
  be 
  verified. 
  In 
  the 
  present 
  

   paper 
  additional 
  examples 
  are 
  quoted, 
  and 
  it 
  is 
  more 
  than 
  

   probable 
  that 
  the 
  list 
  could 
  be 
  extended. 
  For, 
  after 
  the 
  

   general 
  relations 
  of 
  the 
  body 
  became 
  known, 
  I 
  failed 
  to 
  find 
  

  

  