A^knuaryff9oom'}    Contamination  of  Drinking  Water.  33 
in  Uroglena,  but  it  has  a  rather  peculiar  method  of  cell  division 
which  enables  it  to  multiply  rapidly.  Before  a  cell  divides  it  turns 
in  the  periphery  of  the  hollow  gelatinous  sphere,  until  it  is  in  a 
position  at  right  angles  to  the  one  usually  occupied.  Then  at  the 
end  of  the  cell  which  originally  pointed  towards  the  centre  of  the 
sphere  there  are  formed  a  pair  of  cilia  like  those  at  the  opposite 
pole,  and  a  red  spot  appears.  The  cell  then  begins  to  be  sharply 
constricted,  and  as  it  gradually  divides  the  two  halves  are  drawn 
back  through  an  angle  of  45 °,  so  that  when  the  new  cells  are 
finally  formed  they  occupy  a  position  similar  to  the  one  normally 
held  by  the  mother  cell.  When  a  colony  becomes  too  large  it 
breaks  up  into  individual  cells,  and  these  soon,  bv  repeated  division, 
grow  into  new  spheres.  In  addition  to  this  way  of  multiplying, 
resting  spores  are  formed,  which  enables  the  organism  to  survive 
conditions  which  would  otherwise  exterminate  it.  In  this  country, 
Uroglena  seems  to  thrive  best  in  cold  temperatures,  it  usually  occur- 
ring in  greatest  numbers  when  the  water  is  frozen  over.  Just  the 
reverse  is  true  in  Europe,  where  it  is  most  abundant  during  July 
and  August,  and  disappearing  entirely  at  the  approach  of  cold 
weather.  For  a  number  of  reasons  it  seems  probable  that  the 
European  form  is  quite  a  different  species  from  the  one  which  causes 
so  much  trouble  in  America. 
There  are  others  of  the  Syngeneticese  which  contaminate  water, 
although  not  to  the  extent  that  Uroglena  does.  Syniira  and  Syn- 
crypta  are  both  known  to  have  a  bad  effect,  Synura  being  responsible 
for  the  "  ripe  cucumber  "  odor  which  was  formerly  thought  to  be 
caused  by  fresh-water  sponges.  It  is  probable  that  these  two  forms 
are  really  the  same  thing,  and  Dr.  Kirchner,  in  a  note  to  Hansgirg, 
has  said  that  he  united  the  two  under  Synura,  as  he  did  not  consider 
that  a  true  generic  difference  existed  between  them.  The  somewhat 
uncertain  genus  Uvella  should  perhaps  be  mentioned  here.  This 
form,  which  greatly  resembles  Synura,  has  been  reported  as  being 
one  to  be  most  dreaded,  causing  an  exceedingly  disagreeable  taste 
that  was  almost  acid.  Whether  this  organism  really  has  this  effect 
has  been  questioned,  but  it  ought  to  be  watched  for  and  further 
investigations  made. 
Enough  plants  have  been  referred  to  to  make  it  evident  that  in 
dealing  with  such  a  variety  of  forms  having  such  varied  methods  of 
growth  and  reproduction,  it  would  be  quite  impossible  to  have  any 
