1873.] 



Modes of Origin of Infusoria fyc. 



241 



evolution of products of a certain kind. "When prepared with moderately 

 hot water (120° F.), or with cold water (60°-70° F.), the pellicles which 

 are produced become thicker and thicker, and continue for a long time to 

 be soft and pulpy. The changes that may take place in a pellicle of the 

 latter kind are very varied, and they may give rise to a multiplicity of or- 

 ganic forms. 



For a long time my observations were carried on upon infusions made 

 with hot water, and they were also conducted during the winter months, so 

 that the secondary changes which I was able to observe in the pellicle were 

 neither varied nor numerous*. That which is to follow concerning my 

 own observations has been learned from an investigation of the pellicles 

 which form on filtered hay infusions prepared both with warm and with 

 cold water. 



In all cases, and at whatsoever temperature the infusion may have been 

 prepared, the earliest change which takes place in the pellicle is such as I 

 have previously described f . In certain portions of it (altogether irregular 

 in size, shape, and distribution) the aggregated Bacteria begin to form 

 around themselves a certain amount of pellucid gelatinous matter, in which 

 they become imbedded. This change may be well seen in pellicles made 

 with hot water, because such areas continue (more especially when the at- 

 mospheric temperature is low) for several days without undergoing much 

 alteration. The Bacteria in them are slightly separated from one another, 

 rather larger in size, and irregularly placed with regard to the direction of 

 their long axis. Such areas are freely intermixed with other less altered 

 portions in which the Bacteria are densely packed, even smaller than na- 

 tural, and apparently not separated by any pellucid material. Any of the 

 modified areas may after a time undergo changes very similar to those 

 which I described in t Nature ' as resulting in the production of fungus- 

 spores. 



On the other hand, a totally different fate may occasionally await such 

 modified areas. Thus, in a strong infusion prepared with water at a tem- 

 perature of about 120° F., the pellicle was found to be abundant and 

 pulpy ; and on the second day areas of the kind above described w r ere most 



* During this time I was also working at the subject of Archebiosis, and I had not 

 then ascertained that even in this part of the investigation infusions are more efficacious 

 if prepared with moderately hot (120°-130° F.) rather than with very hot water. Tbey 

 answer better wben made with warm water (at the temperature above named) than with 

 cold water, because they can thus be obtained in a more concentrated state. And seeing 

 that in this kind of experiment the fluids have afterwards either to be boiled or other- 

 wise superheated (before or after closure of the flasks), the slight increase in temperature 

 during the preparation of the infusions becomes of less consequence. But in studying 

 Heterogenesis, and with the view of witnessing all the higher changes which may take 

 place in a pellicle, the organic infusions or macerations must be made with cold water } 

 and subsequently filtered, 

 t ' Nature,' no. 35, 1870. 



