206 THE BEGINNINGS OF LIFE. 



generally manifest themselves at the ultimate stage of 

 division, though nothing of this kind shows itself in 

 the more simple process leading to the production of 

 the unicellular organisms.' 



Subsequent experience has abundantly confirmed the 

 truth of the views then expressed, as I have since 

 seen many changes in the pellicle which were strictly 

 intermediate between the extreme forms just described. 

 The characters of the pellicles that form on different 

 hay infusions of the same strength, differ notably 

 according to the temperature of the water with which 

 the infusions have been made, and, to a less extent, 

 according to the mean atmospheric temperature to which 

 they are subsequently exposed. If the infusion has 

 been prepared with very hot water (140? and upwards), 

 only a thin and somewhat tough pellicle will form, 

 secondary changes will take place in it very slowly, 

 and they will lead only to the evolution of products of 

 a certain kind. When prepared with moderately hot 

 water (iaoF) or with cold water (6o 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, so that it may give rise to 

 a multiplicity of organic 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 se- 

 condary changes which I was able to observe in the 



