﻿14 
  W. 
  A. 
  LAMBORX. 
  

  

  of 
  A 
  . 
  albotaeniatus 
  var. 
  montanns, 
  another 
  but 
  rarer 
  bush-breeding 
  species, 
  nine 
  larvae 
  

   of 
  which 
  were 
  brought 
  in 
  at 
  the 
  same 
  time. 
  An 
  examination 
  of 
  the 
  excreta 
  of 
  the 
  

   former 
  showed 
  that 
  digestion 
  must 
  have 
  been 
  largely 
  complete 
  whereas 
  the 
  excreta 
  

   of 
  the 
  latter, 
  though 
  very 
  bulky, 
  consisted 
  almost 
  entirelv 
  of 
  the 
  organism 
  not 
  

   broken 
  up 
  at 
  all. 
  In 
  the 
  laboratory 
  the 
  larvae 
  of 
  A. 
  maculatus 
  and 
  A. 
  karwari 
  

   showed 
  an 
  appreciation 
  as 
  a 
  food 
  of 
  a 
  species 
  of 
  Spirogyra, 
  found 
  usually 
  in 
  the 
  breeding- 
  

   places 
  of 
  the 
  former, 
  and 
  when 
  the 
  filaments 
  were 
  broken 
  up, 
  they 
  could 
  be 
  seen 
  

   nibbling 
  constantly 
  at 
  the 
  broken 
  ends 
  where 
  they 
  reached 
  to 
  the 
  surface. 
  On 
  this 
  

   plant 
  in 
  tap 
  water 
  a 
  small 
  family 
  of 
  A. 
  maculatus 
  was 
  bred 
  to 
  maturitv, 
  but 
  examin- 
  

   ation 
  of 
  the 
  excreta 
  failed 
  to 
  reveal 
  any 
  particles 
  whereby 
  the 
  nature 
  of 
  the 
  food 
  

   could 
  have 
  been 
  determined 
  with 
  certainty. 
  

  

  Without 
  very 
  special 
  knowledge 
  of 
  aquatic 
  micro-organisms 
  it 
  was 
  found 
  

   impossible 
  to 
  arrive 
  at 
  any 
  determination 
  of 
  their 
  character 
  and 
  to 
  decide 
  the 
  

   question 
  of 
  the 
  food 
  preferences, 
  if 
  any, 
  exhibited 
  by 
  larvae. 
  It 
  is, 
  however, 
  well 
  

   recognised 
  that 
  the 
  nature 
  of 
  the 
  algal 
  flora 
  depends 
  very 
  largely 
  on 
  what 
  might 
  

   be 
  considered 
  very 
  small 
  differences 
  in 
  the 
  composition 
  of 
  the 
  water 
  ; 
  differences 
  

   in 
  the 
  nature 
  and 
  amount 
  of 
  salts, 
  and 
  even 
  of 
  the 
  gases 
  present. 
  One 
  finds 
  in 
  

   various 
  works 
  on 
  algae 
  numerous 
  paragraphs 
  emphasising 
  the 
  bearing 
  of 
  such 
  

   differences 
  on 
  the 
  character 
  of 
  algal 
  growths. 
  Since 
  such 
  factors 
  mav 
  well 
  account 
  

   also 
  for 
  the 
  features 
  of 
  larval 
  distribution, 
  it 
  is 
  of 
  value 
  to 
  quote 
  some 
  of 
  the 
  more 
  

   striking 
  observations 
  : 
  — 
  

  

  In 
  the 
  well-known 
  text-book 
  by 
  G. 
  S. 
  West 
  on 
  Algae 
  the 
  following 
  passages 
  

   occur 
  : 
  — 
  

  

  " 
  A 
  careful 
  study 
  of 
  the 
  constituents 
  of 
  the 
  phyto-plankton 
  in 
  relation 
  to 
  the 
  

   lake 
  basins 
  brings 
  with 
  it 
  the 
  conviction 
  that 
  the 
  factor 
  of 
  greatest 
  importance 
  in 
  

   both 
  the 
  qualitative 
  and 
  quantitative 
  distribution 
  of 
  plankton 
  is 
  the 
  amount 
  and 
  

   nature 
  of 
  the 
  dissolved 
  salts 
  present 
  in 
  the 
  water. 
  The 
  highest 
  percentage 
  of 
  dis- 
  

   solved 
  salts 
  is 
  found 
  in 
  those 
  lakes 
  which 
  are 
  contaminated 
  from 
  adjacent 
  farms, 
  

   villages 
  and 
  towns, 
  and 
  such 
  lakes 
  contain 
  a 
  greater 
  bulk 
  of 
  plankton 
  " 
  (p. 
  443). 
  

  

  " 
  Fresh-water 
  algae 
  occupy 
  very 
  varied 
  habitats, 
  and 
  it 
  is 
  because 
  habitat 
  plays 
  

   such 
  an 
  important 
  part 
  in 
  both 
  the 
  occurrence 
  and 
  distribution 
  of 
  fresh-water 
  algae 
  

   that 
  it 
  is 
  here 
  made 
  the 
  basis 
  of 
  the 
  treatment 
  of 
  the 
  subject 
  " 
  (p. 
  418). 
  

  

  " 
  Most 
  of 
  the 
  algal 
  vegetation 
  of 
  fresh 
  waters 
  can 
  be 
  regarded 
  as 
  forming 
  

   associations 
  of 
  a 
  more 
  or 
  less 
  definite 
  character, 
  the 
  peculiarities 
  of 
  which 
  are 
  the 
  

   direct 
  result 
  of 
  habitat, 
  and 
  the 
  nature 
  and 
  amount 
  of 
  the 
  dissolved 
  salts 
  in 
  the 
  

   water." 
  

  

  In 
  a 
  paper 
  by 
  Dr. 
  F. 
  E. 
  Fritsch 
  on 
  the 
  algal 
  flora 
  of 
  Ceylon* 
  one 
  finds 
  the 
  

   following 
  : 
  — 
  

  

  " 
  The 
  character 
  and 
  distribution 
  [of 
  algal 
  vegetation 
  of 
  inland 
  fresh- 
  waters] 
  

   is 
  dependent 
  mainly 
  on 
  temperature, 
  aeration 
  and 
  composition 
  of 
  water" 
  (p. 
  201). 
  

  

  " 
  There 
  are 
  amongst 
  the 
  Algae 
  certain 
  forms 
  which 
  are 
  much 
  more 
  susceptible 
  

   to 
  such 
  variations 
  in 
  environment 
  and 
  which 
  are 
  therefore 
  of 
  more 
  limited 
  distribution, 
  

   and 
  these 
  are 
  the 
  forms 
  which 
  will 
  characterise 
  certain 
  prevailing 
  conditions 
  in 
  the 
  

   surrounding 
  medium. 
  They 
  are 
  character-plants, 
  which 
  will 
  help 
  us 
  to 
  determine 
  

   our 
  aquatic 
  formations, 
  and 
  it 
  is 
  requisite 
  to 
  study 
  them 
  primarilv, 
  and 
  to 
  determine 
  

   the* 
  exact 
  conditions 
  which 
  influence 
  their 
  presence 
  and 
  absence. 
  Other 
  species 
  

   will 
  then 
  be 
  found 
  to 
  be 
  almost 
  constantly 
  associated 
  with 
  these 
  character-plants 
  

   and 
  will 
  make 
  up 
  the 
  subordinate 
  members 
  of 
  the 
  association 
  " 
  (p. 
  202). 
  

  

  * 
  " 
  A 
  General 
  Consideration 
  of 
  the 
  Sub-aerial 
  and 
  Fresh 
  Water 
  Algal 
  Flora 
  of 
  Ceylon." 
  

   Proc. 
  Royal 
  Soc, 
  lxxix, 
  1907. 
  

  

  