472 Prof. H. Marshall Ward. [Dec. 14, 



characters) practically invisible, has occurred without exciting 

 especial comment. B. Greef, in the paper to which I have referred, 

 gives what I take to be a very brief description of the process of 

 aggregation in Epistylis flavicans, and, looking back at observations 

 made on the digestive processes in Amoeba some time ago, I feel that 

 many which were puzzling then are in harmony with the experi- 

 mental results recorded above. Among these I may instance the 

 very sudden quiescence after enclosure of such small organisms as 

 monads, the firm union of unlike ingesta which were by chance 

 enclosed together and so came to be in a common vacuole, and the 

 cohesion after ingestion of particles of carmine or Indian ink. 



And if further work should replace these scattered points of like- 

 ness by fuller, harmonious observations, then I think that the process 

 of aggregation, owing the interest which 'it possesses, not to the 

 obvious movement of particles, but to the more hidden mechanism 

 which carries out the movement, may be allowed to have some such 

 functional value as that indicated in Carchesium by the constancy of 

 its duration and the constancy of its occurrence, whatever the chemi- 

 cal nature of the foreign particles involved. It may perhaps rank 

 as an expression of what has been lacking among the Protozoa what 

 is clear enough among Coelenterata, with their well-defined, uni- 

 cellular giands as an expression of obscure histological change botmd 

 up with the digestion of food, or more nearly with its preparation for 

 digestion. 



II. " The Action of Light on Bacteria. III." By H. MARSHALL 

 WARD, D.Sc., F.R.S., Professor of Botany, Royal Indian 

 Engineering College, Coopers Hill. Received December 14, 



1893. 



(Abstract.) 



Several observers, notably Arloing, Janowsky, Geisler, and 

 Chemelewsky, have tried to determine which rays of the spectrum 

 are chiefly concerned in the destruction of bacteria, but all attempts 

 hitherto have been made by placing separate tubes of broth, gelatine, 

 or potato cultures in the various regions of the spectrum, and judg- 

 ing of the relative rates of growth by the periods in which turbidity 

 is apparent, or by the sizes of the respective growths on solid cultures, 

 and their conclusions vary considerably. 



The author has succeeded in obtaining photographic records by 

 throwing the spectrum on an agar film evenly charged with the 

 spores or bacilli to be investigated, and then observing the behaviour 

 of the illuminated regions after incubation. 



Various species have been employed, Bacillus anthracis, B. sub- 



