[BERKELEY] MARINE BACTERIA 37 



to the formation of phosphatic minerals and fossils. Ammonium 

 magnesium phosphate may easily undergo transformation into 

 calcium phosphate in contact with water charged with calcium 

 bicarbonate and thereby supply an explanation of the deposition of 

 that compound supplementary to that of its derivation from bony 

 material on which attention is usually focussed. 



Broth Agar Plates. 



Each of the broth cultures was plated on Broth-Agar made by 

 adding 2 per cent of Agar to the Broth (reaction unneutralized = + • 3) 

 in order to confirm the purity of the cultures. No. VII failed to grow 

 and on making a subculture into a fresh broth tube (in order to avoid 

 the submission to a high temperature involved in plating) this also 

 failed, showing that the organism had died out. This culture was 

 therefore lost. A typical colony from each plate was subcultured on 

 to a slope of the same medium. In only one case was more than one 

 type of colony obtained, that of Culture I. In this case each type was 

 subcultured (Cultures I A and IB respectively). 



Broth Agar Slopes. 



The characteristics of the cultures obtained on Broth-Agar slopes 

 could be divided into four classes to one or other of which all the 

 cultures, except two (Nos. XV and XXVIII), conformed very nearly. 

 These classes are designated in the table of characteristics as A B, C, 

 and D respectively. They may be described as follows : — 



Class A. Fairly dry, slightly spreading, grayish white, trans- 

 parent. 



Class B Dry, confined, white, opaque. 



Class C. Moist, spreading, grayish yellow, transparent. 



Class D. Fairly dry, confined, yellow, transparent. 



fn many of the cultures large crystals, similar to those formed in 

 the broth media, were found imbedded in the Agar after a month 

 or so. They were separated, by dissolving the medium in hot water 

 and centrifugalizing hot, and were found to have the same crystalline 

 form and qualitative chemical composition as those isolated from 

 broth 



Films from each of the Agar cultures were made and stained in 

 the routine manner as soon as growth was well established. A second 

 series was made a few days later and stained by Gram's method. 

 Where the organism failed to stain by this method the ordinary 

 staining was repeated in order to note any change that took place in 

 the morphology of the organism with age. 



