[BERKELEY] MARINE BACTERIA 39 



the independence of this precipitation on nitrite or ammonia produc- 

 tion. The absence of alkaHnit}^ to phenolphthalein in some of the 

 cultures in Medium C in spite of their showing an ammonia reaction 

 must be due to the ammonia being completely neutralized by the acid 

 displaced from the calcium acetate or by carbonic acid, so that it is 

 present only as acetate or bicarbonate. 



Another point of interest in connection with these cultures is 

 that nitrite is produced by many of the organisms in Medium B, but 

 not in Medium C. This seems to indicate that, although these 

 organisms can break down nitrate to obtain their nitrogen, they do 

 so only in the absence of such complex organic nitrogen compounds 

 as peptone. 



Similarities Amongst the Organisms Isolated 



Each culture whose characteristics are described in the annexed 

 table originated from a single colony from a plate showing colonies of 

 only one kind, and this plate was itself derived from a culture obtained 

 from a single colony on a previous plate. There can therefore be 

 little doubt as to the purity of the cultures. The variation in form 

 seen in many of the cultures both in Broth and on Agar can therefore 

 be attributed to nothing but polymorphism on the part of the organ- 

 isms so that the miscrocopic form is of little service in establishing 

 identities between the various cultures. For this reason the measure- 

 ments given were not determined in specially carefully fixed specimens. 

 They should, however, be comparable amongst themselves since all 

 were fixed and stained under like conditions. The forms in cultures 

 having quite different growth characteristics showed in many cases 

 close approximation to one another, there was in fact frequently as 

 close agreement in form and size between the organisms in two different 

 cultures as there was between the individuals in either of them. The 

 age of the culture also made a very considerable difference in the size 

 of the organisms found in it. In many cases, for instance, the agar 

 culture when examined at two or three days old showed an organism 

 nearly twice as long as any found when the same culture was examined 

 a few days later when testing the ability of the organism to stain by 

 Gram's method. The size of the organism has therefore been taken 

 into account only in the most general way in endeavouring to establish 

 identities between the various cultures. 



Chiefly therefore from a consideration of the other characteristics 

 it is considered that the following cultures are identical or very nearly 

 allied forms: — 



