The  following  instance  gives  an  example  of  local  distribu-
tion of  an  organism  in  swarms,  and  of  the  erroneous  conclusions
that  might  be  drawn  from  imperfect  or  incomplete  observations  :

"  We  were  fortunate  enough  on  one  occasion  to  obtain
incontrovertible  evidence  of  the  sharply  defined  nature  of  a
shoal  of  organisms,  forming  an  instructive  example  of  how
nets  hauled  under  similar  circumstances  a  short  distance  apart
may  give  very  different  results.  On  the  evening  of  April  1st
(1907),  at  the  'alongshore'  Station  III.,  north  of  Port  Erin,
off  the  '  Cronk  '  one  mile  out,  I  took  six  simultaneous  gatherings
in  both  surface  and  deeper  waters.  Two  of  the  nets  were  the
exactly  similar  surface  tow-nets  which  I  have  called  B  and  C.
At  half-time,  as  the  result  of  a  sudden  thought  I  hauled  in  B,
emptied  the  contents  into  a  jar,  and  promptly  put  the  net  out
again.  This  half  gathering  was  of  very  ordinary  character,
containing  a  few  Copepoda,  some  Diatoms  and  some  larvae,
but  no  Crab  Zoeas.  At  the  end  of  the  15  minutes,  when  all  the
nets  were  hauled  on  board,  all  the  gatherings,  including  B,
showed  an  extraordinary  number  of  Crab  Zoeas  rendering  the
ends  of  the  nets  quite  dark  in  colour.  B  was  practically  the
same  as  C  although  B  had  only  been  fishing  for  seven  minutes.
