FIG 108. 



Cellular Plants. 249 



could not be predicted what sort of an effect a change of environment 

 might have on them ; nor could any reason be antecedently assigned 



. . .< . 'CL 6. ..*.". *.-. FIG. 108. Development of Monad (Nonas lens) 

 fr m a pellicle formed on an infusion of Lay in six 



a ' ^' c. Quiescent stages of development. 

 d Flagellum vibratile and Monad active. (Mag- 

 nified 1800 diameters.) 



The size of the Monads d is 1-2500 of an inch. 

 (After Pouchet.) 



why these masses, so active in the cells of 

 the plant, should not be active in another 

 medium, giving equal or greater freedom 

 to their movements. I do not regard this 

 as a case of " spontaneous generation," or 

 generation de novo, but simply a transfer 

 of living from one environment to another, 

 and a new development appropriate to and in consequence of the new 

 conditions. The same theory applies to most of the life development 

 from infusions of organic elements. New habits of life are imposed 

 upon old organic materials. The theory accounts for the development of 

 many of the numerous forms of low life that follow upon the death of 

 an} 7 highly developed organism. The air may carry occasional germs of 

 HVP or dead, green or dry ferments, that may at times originate develop- 

 ment in infusions, but it is incredible that the air is everywhere burdened 

 with the germs of thousands of species and varieties of organic life. 



FIG. 109. Dust from the Air. 



Collected by Pasteur, and 

 found to contain Organic mat- 

 ter, Germs, &c. ( Greatly mag- 

 nified.) 



a. Collected June, 1860. 



&.__ January, 1861. 



On this subject M. Pasteur says: " In conclusion, we see that ordi- 

 nary air contains only here and there, and with no continuity, the neces- 

 sary condition for the initiation of the so-called spontaneous generation. 

 Here there are germs, whilst in immediately adjoining portions of the 

 atmosphere there are none. Further on there are other kinds of germs, 

 and there are few or many of them, according to the nature of the lo- 

 cality." 



M. Pouchet also examined the air by the most approved methods, 

 and found large quantities of debris, both mineral and organic. He 

 found granules of starch abundantly scattered about, plenty of epi- 

 dermic tissue and particles of chlorophyl. Of spores of fungoid bodies 



