ATMOSPHERIC MICROORAPHY. 171 



forming, as might be expected, a more decided feature than 

 in the deposits derived at once from the air. The conclusions 

 at which Dr. Cunningham arrived are the following : 



1. Specimens of rain-water in Calcutta, collected with every 

 precaution to ensure their freedom from contact, contamina- 

 tion, sooner or later, frequently show the presence of spores, 

 mycelium, zoospores, monads, bacterioid bodies, and distinct 

 bacteria. 



2. They do not, as a rule, contain any of the higher forms 

 of infusoria. 



S. The zoospores are demonstrably derived from the my- 

 celium arising from common atmospheric spores. 



4. There is every probability that the monads and bacteria 

 have a similar origin, but it remains quite uncertain whether 

 their development is due to heterogenesis or to the presence 

 of their germs within the parent cells, or as the result of a 

 process of normal development in the latter. 



The above is but a slight sketch of a most interesting 

 memoir, every page of which deserves careful attention. 



