SEA-FISHERIES LABORATORY. 123 



(1) The Identity of the Micro -Organisms isolated. 



There has been no opportunity for making a systematic 

 and prolonged investigation of the species of lactose-fermenting 

 bacteria inhabiting shellfish, and the data given in the following 

 tables are only those obtained in the routine examination of 

 samples which were examined with special objects in view. 

 The regular method adopted in these analyses was to make 

 an emulsion of the soft parts of five mussels, and then make 

 up this emulsion with sterile water to a volume of 250 c.c. 

 One c.c, containing l/50th part of a single mussel, was then 

 plated in neutral-red, bile salt, lactose agar and incubated 

 at 37° C. for 24 hours. Five such plates were usually made, so 

 as to get a reliable mean estimate of the numbers of lactose- 

 fermenting organisms per mussel. A number of colonies from 

 each plate were then isolated and subcultures were made on 

 nutrient agar. After incubation, for a period of 4 to 6 hours, 

 the motility, or lack of motility, of the organisms was observed, 

 and after further incubation for 2 days the fermentation tests 

 were applied. The various media were inoculated and 

 incubated for 4 days before the results were recorded. The 

 symbol + m the tables means that acid and gas formation 

 took place in the sugars ; that a distinct pink colour was 

 observed in a peptone water culture on the addition of 

 paradimethylamidobenzaldehyde (the method being that of 

 Marshall, Journal of Hygiene, Vol. VII, p. 581) ; and that a 

 peptone-glucose culture became pink within 24 hours after the 

 addition of strong caustic potash solution. If a sugar medium 

 was merely discoloured, or rendered acid, without gas formation, 

 the reaction is described as negative. These results are clear 

 and definite, but this is hardly the case with the observations 

 of the presence or absence of motility in the organisms studied. 

 Sometimes there was no doubt at all whether or not an organism 

 was motile or immotile, but in very many cases it was not easy 

 to be certain. In the attempt to identify the various organisms 



