THE BEGINNINGS OF LIFE. 207 



pellicle were neither varied nor numerous '. That which 

 is to follow in this chapter concerning my own obser- 

 vations, has been learned from an investigation of the 

 changes in pellicles which form on filtered hay infusions 

 prepared both with warm and with cold water. 



In all cases, and at whatsoever temperature the in- 

 fusion may have been prepared, the earliest change 

 which takes place in the pellicle is such as I have 

 previously described. In certain portions of it alto- 

 gether 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 atmo- 

 spheric temperature is low) for several days without 

 undergoing much alteration. The Bacteria in them are 

 slightly separated from one another, rather larger in 



1 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 

 I30F) rather than with very hot water. They answer better when 

 made with hot 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 otherwise superheated (before or after closure of 

 the flasks), the slight increase in temperature during the preparation 

 of infusions becomes of less consequence. But in studying Hetero- 

 genesis, 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. 



