NOTES. 
THE FORMATION OF BACTERIAL COLONIES '.—During 
the detailed examination of a large number of forms or species of 
Bacteria from the Thames, I have been struck, as have other investi- 
gators, with the extreme difficulty — not to say impossibility— of 
successfully employing the diagnoses given in authoritative works, 
such as Eisenberg’s Bakteriologische Diagnostik. Over and over again 
pronged cultures of a given form showed departures in sometimes 
one and sometimes another direction ; and although the generality of 
the characters sufficed to diagnose a type nearer to one or another of 
the accepted ‘ species,’ the variations were so numerous that it was 
difficult to do anything with them beyond describing all the ‘ varieties/ 
This was not due to differences in the cultures in the ordinarily 
accepted meaning of the word, because half a dozen forms of the same 
type varied when cultivated side by side in the same media, and 
consequently it was impossible to admit that differences in the 
conditions of culture (in the ordinarily accepted meaning of the term) 
were responsible. 
The suspicion therefore arose that one and the same ‘ species ’ of 
Bacterium will differ in its behaviour according to the vicissitudes it 
has been subjected to in the river previously to its capture : in other 
words, that ‘ varietal ’ forms occur stamped for the time being with 
acquired characters. 
On the other hand, the possibility existed that in cultures side by 
side, assumed to be identical, and still more in the case of cultures in 
media prepared according to the same formula but at different times — 
e.g. two brews of peptone-gelatine, or two potato-tubes prepared from 
different potatoes— causes of variation might exist far too subtle for 
detection, but which nevertheless have their effect on the sensitive 
organization of the Schizomycetes. 
Consequently I attempted the task of cultivating gelatine-plate- 
colonies under such circumstances that the very earliest stages of 
development could be observed directly under the highest powers of 
the microscope, so as to see how colonies are built up from the first 
division of a Bacillus until the usual macroscopic characters of the 
colony are recognizable, as in ordinary plate-cultures. 
This was done by isolating simple Bacteria in a hanging drop of 
1 Read before the Botanical Section of the British Association at Ipswich. 
