592 
droppings  of  birds  of  the  carrion-feeding  kind.  This  belief  consider¬ 
ably  influenced  some  authorities  against  rigorously  protecting  Uieir 
water  supplies  from  mosquitos,  and  it  was  therefore  with  the  object 
of  testing  whether  there  was  any  foundation  for  this  belief  and  with 
the  further  object  of  studying  the  effect  of  minute  forms  of  animal 
life  on  drinking  water — such  forms,  for  example,  as  are  found  in  large 
numbers  in  tlie  filter  beds  and  reseiwoirs  of  the  water  supplies  of 
cities — that  I  undertook  with  my  Assistant,  Mr.  Frederick  C.  Lewis, 
the  following  series  of  simple  experiments:  — 
The  experiments  consisted  in  placing  larvae  of  Ciilc.x  spp. 
and  of  Jhcobaldia  annulata  in  a  flask  of  non-sterilised  drinking 
water,  and  comparing  from  day  to  day  the  number  of  bacteria  present 
m  the  water  with  the  number  present  in  a  control  flask  to  which  no 
larvae  had  been  added.  The  two  flasks  which  1  call  'A'  and  ‘B’ 
were  freely  exposed  to  the  air.  The  number  of  bacteria  was 
estimated  by  plating  r  c.c.  of  the  w^ater  in  gelatine  and  incubating  at 
21°  C.  for  72  hours. 
'Fhe  results  were  as  follows  :  — 
Skrif.s  T 
Date 
T''i..v.k  ‘A,’  without  larvae 
Flask  '  R/  with  larvae 
1 
Bacteria  per  i  c.c. 
I 
1  Bacteria  per  i  c.c. 
4.12.09 
880 
873 
V 1 2.09 
983 
1.93.3 
6.12.09 
U350 
2.720 
7.12.09 
r.420 
2,390 
8.12.09 
765 
3.597 
9.12.09 
980 
5.390 
1 0. 1 2.09 
— 
1 1. 12.09 
15 
— 
I  2. 1  2.09 
35 
9.370 
Series  11 
Date 
4.12.09 
5.IZ.09 
6.12.09 
7.12.09 
8. 1 2.09 
9.12.09 
10. 12.09 
1 1. 12.09 
T  2. 1 2.09 
1 
Flask  ‘  A,'  without  larvae 
Flask  ‘  1?,’  with  larvae 
Bacteria  per  c.c. 
- - — 
Bacteria  per  c.c. 
28.1.10 
25 
1,250 
29.1.10 
1  •  t  .J 
109 
8,600 
30.1. 10 
31. 1. 10 
599 
51,200 
31. 1. 10 
1.2. 10 
3.090 
67,000 
r.2.10 
137,000 
3,2.10 
