SEA-FISHERIES LABORATORY. 145 
Where “ dilution 0 ” represents 1 c.c. of a liquid suspension, 
made as indicated above, and is taken as equivalent to 1/50th 
part of an average mussel. The sign “+ ” represents forma- 
tion of acid and gas in the bile-salt broth; “a” represents 
formation of acid only, and the negative sign indicates absence 
of any reaction. 
(2) lc.e. polluted sea-water hg are > te Ge 
1/10th _, us et etal le idl bist km ra 
3) le.c. polluted water =e Fi oc: ++ a-—— 
1/10th 99 - FUN o-euani to a ere 
1/100th_—si,, : el ae OM Fee es 
(4) lc.c. polluted water ne ay. sti +++4++ 
1/10th 9 35 auie sale ies ++4+4+4+ 
1/100th ” ” sae she Ste Be io es 
1/1,000th ,, ss a 3 be +aaa— 
1/10,000th ? 9 see see ace a----— 
(5) 1lc.e. polluted water a re he +++++ 
1/10th ”» % ine aie oa ee ee 
1/1,000th 9 wert) cee pee siege i AR Gil” eg eee’ yes Bias 
(6) 1c.e. polluted water vk Leis ee $F+¢4+4+44+4+4+4+4+ 
1/10th We sep 3a te wo t+taadaaa-—-—-— 
1/100th_—s,, 9 = ahs A a na gee a A 
In all these examples the tubes were incubated for 24 
hours. In the following experiment the tubes were incubated 
for 4 days, and “ read” at intervals of 24 hours :— 
1 Day. 2 Days. 3 Days. 4 Days. 
(7) 1/50 mussel 5+ 5+ 5+ 5+ 
1/500 * 44+,1— 4+,1— 44+,1- ‘44+,1- 
1/5,000 A o+,3— 5+ 5+ 5+ 
1/50,000 si, 5 — 1+,2a,2-— 1+,2a,2- 1+, 3a,1—- 
1/500,000_,, 5— 5 — l+,4— 1+,4-— 
1/5,000,000 ,, 5— 5 — 5- 5 — 
Now all these tests, simple and conclusive as they may 
appear to be when only one culture from each dilution is made, 
become more difficult to interpret when they are so made that 
