Report to the Water Research Committee. 



415 



precisely the same way with the spark spectrum as with the flame 

 spectrum, and that the red cadmium line behaves in the same way 

 as the others. The magnetic effect is better seen, from a direction 

 perpendicular to the line of force, when a nicol is interposed in the 

 path of the light, but rotation of the nicol through 90° cuts it 

 entirely off, accurately so when a small spark is the source of 

 light.— May 31.] 



Fifth Report to the Royal Society Water Research 

 Committee. 



By H. Maeshall Ward, Sc.D., F.R.S., F.L.S., Professor of Botany 

 in the University of Cambridge. Presented to the President and 

 Council, December 10, 1896. 



(Abstract.) 



The following is a short resume of the principal points resulting 

 from three years' study of the Bacterial Flora of the Thames. 



All the forms have been grown on gelatine, agar, and potato, as well 

 as in broth, milk, and sugar-solutions, and some of them in special 

 media in addition. Moreover, most of them have been cultivated in 

 hanging drops under the microscope, sometimes isolated and under 

 high powers, for long periods, and the course of development of the 

 colonies traced in detail in several cases, and even when this could 

 not be successfully carried to a conclusion, information as to the 

 changes and growth of the organisms has been obtained, which helps 

 to throw light on their behaviour and relationships. 



This work has occupied a long time, and these water bacteria do 

 little beyond growing and dividing, so that in many respects this 

 part of the work only starts problems for the future. In some cases, 

 however, the morphological changes observed are helpful in explain- 

 ing the macroscopic appearances of the colonies, and in any case it is 

 clear that no examination of a bacterium can be considered complete 

 until its life-history has been traced under the microscope. 



The number of forms isolated and cultivated amount to eighty, nob 

 counting the large number which were either rejected at an early 

 stage as certainly duplicates, or lost during cultivation. 



Of these eighty forms some have been distinctly recognised as well 

 known types, e.g., Bacillus membranaceus amethystinus (Eis.), B. 

 fluorescens liquefaciens (FL), B. Jluorescens non-liquefaciens (PI.), B. 

 coli commune, Proteus vulgaris (Haus.), Bacillus arborescens (Fr.), 

 B. prodigiosus (Ehr), B. termo (Cohn), B. subtilis, and Sarcina lutea. 



