76 THE FACTORS OP ORGANIC EVOLUTION. 



1878. It was a continuation of a preceding paper which, 

 referring chiefly to Bacteria, contended that 



&quot;Light is inimical to, and under favourable conditions may wholly prevent, 

 the development of these organisms.&quot; 



This supplementary paper goes on to show that the injurious 

 effect of light upon protoplasm results only in presence of 

 oxygen. Taking first a comparatively simple type of molecule 

 which enters into the composition of organic matter, the 

 authors say, after detailing experiments : 



&quot; It was evident, therefore, that oxyyen was the agent of destruction under 

 the influence of sunlight.&quot; 



And accounts of experiments upon minute organisms are 

 followed by the sentence 



&quot; It seemed, therefore, that in absence of an atmosphere, light failed 

 entirely to produce any effect on such organisms as were able to appear.&quot; 

 They sum up the results of their experiments in the 

 paragraph 



&quot; We conclude, therefore, both from analogy and from direct experiment, 

 that the observed action on these organisms is not dependent on light per se t 

 but that the presence of free oxygen is necessary ; light and oxygen 

 together accomplishing what neither can do alone : and the inference 

 seems irresistible that the effect produced is a gradual oxidation of the 

 constituent protoplasm of these organisms, and that, in this respect, 

 protoplasm, although living, is not exempt from laws which appear to 

 govern the relations of light and oxygen to forms of matter less highly 

 endowed. A force which is indirectly absolutely essential to life as we know 

 it, and matter in the absence of which life has not yet been proved to exist, 

 here unite for its destruction.&quot; 



What is the obvious implication ? If oxygen in presence 

 of light destroys one of these minutest portions of protoplasm, 

 what will be its effect on a larger portion of protoplasm ? 

 It will work an effect on the surface instead of on the whole 

 mass. Not like the minutest mass made inert all through, 

 the larger mass will be made inert only on its outside; 

 and, indeed, the like will happen with the minutest mass if 

 the light or the oxygen is very small in quantity. Hence 

 there will result an envelope of changed matter, inclosing 

 and protecting the unchanged protoplasm there will 

 result a rudimentary cell-wall. 



