COLON-AEROGENES FORMS FROM NATURAL WATERS 61 



be noted that members of the same provisional group show con- 

 siderable divergence in their ability to react with sugars, etc., 

 and with gelatine. If these variations are made the basis of 

 subdivision, the number of provisional groups is increased, as 

 indicated by literal suffixes to the reference numbers in table 3. 

 The cultures are arranged as before, primarily with regard to 

 their lactose, uric acid and adonitol reactions, then with 

 reference to sucrose, dulcitol and glycerol. 



For the sake of conciseness the reactions of strains are repre- 

 sented so far as is possible by the numerical scheme of the 

 Society's chart, with the addition of methyl red and Voges- 

 Proskauer reactions in standard media and a few other reactions. 

 Maltose and mannitol were fermented with gas formation by all 

 strains except 17, 18a and 18b, Starch was attacked with gas 

 formation by but 2 strains, and those were gporeformers. Gela- 

 tine was liquefied by 10c and by 5 sporeformers. Raffinose and 

 sucrose reactions were of like signs for all save 5b and 10a. 



The inclusion of sporebearing forms in this table is anticipated 

 by the work of Loehnis and Smith (1916), who state that a single 

 species (particularly Azotobacter) may pass through as many as 

 12 to 14 distinct morphological forms in its life cycle, including 

 spores. Kellermann and Scales (1916), in a preliminary report 

 on the life cycle of Bad. coli, studied 12 strains from widely 

 different sources which were found to produce all the types 

 described by Loehnis and Smith except spores. Burton and 

 Rettger report 9 occurrences of a form differing chiefly from our 

 No. 15 in that theirs is Gram positive. Meyer (1918) and 

 Ewing (1919) isolated from waters a spore-bearing, lactose-fer- 

 menting, acid-forming bacillus which seems identical with our 

 16b. Itano and Neill (1919) found sporeformation by B. subiilis 

 to be a function of temperature and hydrogen ion concentration : 

 it is possible that unfavorable environment may lead to spore- 

 formation by members of the colon-aerogenes group. 



Methyl red reactions in different concentrations of Difco pep- 

 tone varied upon repetition. The strains grouped under num- 

 bers 4 to 9 inclusive gave slightly more methyl red positive reac- 

 tions with the 0.5 per cent Witte peptone broth" incubated for 5 



