﻿396 
  JOHN 
  RENNIE. 
  

  

  could 
  be 
  seen 
  to 
  be 
  continuous 
  wibli 
  the 
  other, 
  sometimes 
  a 
  

   dark 
  column 
  merged 
  with 
  a 
  light, 
  or 
  dark 
  cells 
  occurred 
  ou 
  

   one 
  side 
  of 
  a 
  capillary 
  and 
  light 
  ones 
  on 
  the 
  other. 
  I 
  am 
  not 
  

   sure 
  that 
  there 
  is 
  much 
  in 
  this, 
  but 
  in 
  any 
  case 
  he 
  does 
  not 
  

   appear 
  to 
  have 
  observed 
  the 
  contrast 
  in 
  grouping 
  of 
  the 
  two 
  

   sets 
  as 
  noted 
  by 
  me, 
  e. 
  g. 
  in 
  Pleuronectes, 
  nor 
  the 
  relative 
  

   distribution 
  of 
  the 
  capillai-ies 
  of 
  the 
  two 
  regions. 
  In 
  this 
  

   species 
  I 
  found 
  the 
  capillaries 
  more 
  abundant 
  in 
  the 
  inner 
  

   regions, 
  and 
  here 
  the 
  columnar 
  cells 
  were 
  most 
  noticeable, 
  

   while 
  the 
  other 
  type 
  occupied 
  along 
  with 
  the 
  capillaries 
  the 
  

   spaces 
  between 
  and 
  also 
  the 
  surrounding 
  areas. 
  In 
  Zoarces 
  

   the 
  arrangement 
  suggested 
  by 
  the 
  grouping 
  was 
  that 
  of 
  

   columns 
  of 
  cells 
  with 
  an 
  interstitial 
  tissue. 
  It 
  is 
  true 
  that 
  the 
  

   columnar 
  arrangement 
  is 
  due 
  probably 
  to 
  the 
  abundance 
  of 
  

   the 
  capillaries, 
  whose 
  course 
  the 
  cells 
  follow; 
  but 
  if 
  they 
  are 
  

   all 
  one 
  tissue 
  I 
  have 
  been 
  unfortunate, 
  as 
  also 
  has 
  Massari, 
  in 
  

   seeing 
  preparations 
  which 
  exhibited 
  the 
  columnar 
  cells 
  in 
  one 
  

   phase 
  only, 
  and 
  that 
  different 
  from 
  the 
  rest 
  of 
  the 
  islet. 
  

   Diamare 
  himself 
  compares 
  the 
  appearance 
  of 
  an 
  islet 
  in 
  

   Motella 
  to 
  the 
  supra-renals 
  of 
  birds, 
  where 
  the 
  cortical 
  and 
  

   medullary 
  substances 
  interlace. 
  

  

  I 
  examined 
  some 
  very 
  small 
  islets 
  in 
  Ammodytes 
  and 
  

   Pleuronectes 
  where 
  there 
  was 
  only 
  a 
  limited 
  number 
  of 
  cells 
  

   visible 
  in 
  a 
  section. 
  They 
  were 
  so 
  small 
  that 
  a 
  difference 
  of 
  

   functional 
  state 
  between 
  different 
  parts 
  was 
  scarcely 
  to 
  be 
  

   looked 
  for, 
  and 
  yet 
  the 
  two 
  types 
  were 
  apparent 
  (fig. 
  6, 
  Sm. 
  

   is, 
  and 
  Is. 
  3). 
  

  

  Although 
  I 
  incline 
  to 
  the 
  view 
  that 
  we 
  have 
  here 
  two 
  

   distinct 
  tissues, 
  from 
  a 
  consideration 
  of 
  the 
  fact 
  that 
  in 
  many 
  

   species 
  this 
  double 
  nature 
  is 
  not 
  evident, 
  I 
  do 
  not 
  think 
  they 
  

   are 
  likely 
  to 
  be 
  of 
  independent 
  secreting 
  function. 
  The 
  dark 
  

   cells 
  appear 
  to 
  stand 
  in 
  a 
  relation 
  intermediate 
  to 
  the 
  

   capillaries 
  on 
  the 
  one 
  hand 
  and 
  the 
  light-cells 
  on 
  the 
  other. 
  

   It 
  may 
  be 
  that 
  they 
  regulate 
  the 
  supply 
  to 
  the 
  capillaries 
  of 
  

   the 
  substance 
  secreted 
  by 
  the 
  light-cells, 
  or 
  they 
  may 
  effect 
  a 
  

   final 
  stage 
  in 
  its 
  elaboration. 
  

  

  