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THE BEGINNINGS OF LIFE. 



179 



of the old vitalistic theories which may now be lopped 

 off without further concern— leaving us no other life- 

 factors in the case of these lowest organisms than the 

 organic matter and the external conditions or incident 



physical forces. 



But let us glance more briefly at the doctrines of two 



Needham 



Miiller 



lists of his time^ was also a believer in the spontaneous 

 generation of the lower kinds of organisms. On the 

 present aspect of our subject he expresses himself most 

 distinctly thus ^:—^ Animals and vegetables decompose 

 into organic particles, endowed with a certain degree 

 of vitality, and constituting the simplest animalcules, 

 which are capable of developing, either after the fashion 

 of germs, by union with other particles, or by themselves 

 contributing towards the development of some other 

 animal — only to become free again after its death, and 

 to recommence eternally a similar cycle of mutations.' 

 At the commencement of the present century, also, 

 Treviranus ^ expressed his belief in the existence of a 

 primitive amorphous organic matter — a plastic material 

 which was ready to assume all the forms met with in 

 living things, and which was most prone to alter its 

 present pattern under the powerfully modifying in- 

 fluence of a change in the conditions of its existence. 



1 ( 



1787. 



2 < 



Aninialcula infusoria, fluviatilia et marina/ &c. Opus posth. Leipzig, 



Biologic/ Gottingen, 1802, torn. ii. pp. 267, 403. 



N 2 



