﻿66 
  Miscellaneous. 
  

  

  I 
  will 
  add 
  one 
  unpublished 
  observation 
  to 
  the 
  well-known 
  facts 
  here 
  

   brought 
  together. 
  Two 
  sporanges 
  of 
  Saprolegnia 
  opened 
  at 
  an 
  early 
  

   stage 
  of 
  the 
  partial 
  segregation 
  of 
  the 
  protoplasm 
  into 
  masses. 
  Part 
  

   of 
  the 
  protoplasm 
  in 
  each 
  slowly 
  escaped 
  and 
  aggregated 
  into 
  rounded 
  

   masses. 
  The 
  first 
  discharged 
  masses 
  underwent 
  the 
  usual 
  patho- 
  

   logical 
  changes 
  and 
  diffluence 
  ; 
  the 
  later 
  masses 
  (from 
  both 
  sporangia) 
  

   had 
  already 
  acquired 
  the 
  power 
  of 
  forming 
  contractile 
  vacuoles 
  pos- 
  

   sessed 
  by 
  the 
  zoospores 
  ; 
  the 
  numerous 
  small 
  vacuoles 
  appeared 
  and 
  

   contracted 
  regularly, 
  lines 
  of 
  separation 
  formed 
  and 
  deepened, 
  and 
  

   the 
  masses 
  divided 
  into 
  zoospores, 
  which 
  separated 
  and 
  swarmed, 
  

   just 
  like 
  the 
  protoplasm 
  which 
  remained 
  in 
  the 
  sporange, 
  though 
  

   more 
  slowly. 
  This 
  observation 
  seems 
  to 
  afford 
  a 
  crucial 
  test 
  of 
  the 
  

   truth 
  of 
  the 
  thesis 
  that 
  the 
  contractile 
  vacuole 
  has 
  the 
  function 
  of 
  

   preventing 
  excessive 
  vacuolation 
  and 
  diffluence 
  of 
  naked 
  cells 
  in 
  

   water. 
  

  

  The 
  following 
  is 
  a 
  brief 
  summary 
  of 
  the 
  points 
  on 
  which 
  the 
  above 
  

   thesis 
  rests 
  : 
  — 
  

  

  1. 
  All 
  naked 
  protoplasmic 
  bodies 
  living 
  in 
  fresh 
  water 
  have 
  at 
  

   least 
  one 
  contractile 
  vacuole. 
  

  

  2. 
  The 
  possession 
  of 
  this 
  is 
  quite 
  independent 
  of 
  the 
  systematic 
  

   position 
  of 
  the 
  organism 
  and 
  of 
  the 
  presence 
  of 
  chlorophyll 
  *. 
  

  

  3. 
  The 
  vacuole 
  loses 
  its 
  contractility 
  on 
  the 
  formation 
  of 
  a 
  strong 
  

   cell-wall 
  or 
  cyst, 
  and 
  may 
  even 
  disappear. 
  

  

  4. 
  It 
  is 
  absent 
  from 
  Gregarinida 
  and 
  Opalina 
  and 
  the 
  Badiolaria 
  

   which 
  inhabit 
  saline 
  liquids. 
  

  

  5. 
  When, 
  owing 
  to 
  morbid 
  conditions, 
  the 
  efficiency 
  of 
  the 
  con- 
  

   tractile 
  vacuole 
  is 
  impaired, 
  excessive 
  vacuolation 
  and 
  diffluence 
  

   ensue. 
  

  

  0. 
  Conversely, 
  as 
  soon 
  as 
  contractile 
  vacuoles 
  appear, 
  the 
  tendency 
  

   to 
  excessive 
  vacuolation 
  and 
  diffluence 
  is 
  arrested. 
  

  

  It 
  may 
  be 
  suggested 
  that 
  the 
  perforations 
  of 
  the 
  nephridial 
  cells 
  

   in 
  Vermes 
  and 
  embryonic 
  mollusks 
  and 
  of 
  the 
  epiblastic 
  gland-cells 
  

   of 
  Vermes 
  and 
  Arthropods 
  are 
  due 
  to 
  the 
  persistence 
  of 
  the 
  con- 
  

   tractile 
  vacuole, 
  the 
  opening 
  of 
  which 
  has 
  become 
  permanent, 
  while 
  

   its 
  contractility 
  has 
  been 
  superseded 
  in 
  the 
  kidneys 
  at 
  least 
  by 
  other 
  

   arrangements. 
  Even 
  the 
  goblet-cells 
  of 
  mucous 
  epithelia 
  may 
  

   possibly 
  be 
  traced 
  to 
  this 
  origin. 
  

  

  On 
  Adelphotaxy, 
  an 
  undescribed 
  Form 
  of 
  Irritability. 
  

   By 
  Professor 
  Marcus 
  M. 
  Hartog, 
  D.tSc, 
  M.A.f 
  

  

  In 
  Achhja, 
  a 
  genus 
  of 
  Saprolegnieae, 
  the 
  zoospores 
  lie 
  in 
  the 
  

   6porange 
  before 
  liberation 
  closely 
  appressed 
  together, 
  with 
  their 
  long 
  

   axes 
  parallel, 
  instead 
  of 
  showing 
  the 
  rotatory 
  hustling 
  movements 
  

   of 
  other 
  species. 
  On 
  liberation, 
  instead 
  of 
  separating 
  and 
  swimming 
  

  

  * 
  Hence 
  the 
  function 
  canuot 
  be 
  exclusively 
  respiratory, 
  though 
  it 
  may 
  

   aid 
  respiration. 
  

  

  t 
  Read 
  at 
  the 
  British 
  Association 
  (Bath), 
  1888. 
  

  

  