THE BEGINNINGS OF LIFE. 303 



ganisms which reveal themselves and, similarly, when 

 solid portions of organic matter are immersed in solu- 

 tions, different results are produced by their immersion 

 at various depths ] . Abundant evidence of such facts 

 may also be gathered from what has been stated con- 

 cerning my own experiments. Again, the boiling or not 

 of the organic solution, as we have seen, has a very great 

 influence over the kinds of organisms, as well as over 

 the rapidity with which they appear 2 . It has, more- 

 over, been ascertained that differences in the amount 

 of heat and electricity, and in the kind and degree of 

 light, which are allowed to operate upon the various 

 fluids, are all more or less influential, and exercise a most 

 undoubted influence over the kinds of organisms that are 

 to be met with in different cases. So that the amount 

 and kind of modification which is capable of being 

 brought about in the living forms that are to appear 

 in different infusions made with the same water and 

 exposed to the influence of the same air, are of such 

 a nature as strongly to encourage the belief that such 

 living forms cannot to any appreciable extent be derived 

 either from the air or from the water. 



In illustrating this part of the argument which has 

 reference to the development of organisms in solutions 

 exposed to the air, we have purposely laid most stress 

 upon the mode of origin of the ciliated Infusoria rather 



1 See Pouchet's ' Heterogenie,' pp. 154-159- 



2 See also Pouchet, loc. cit., pp. 148-150. 



