172 HETEROGENETIC ORIGIN OF 



Before citing some experimental results bearing upon this point I 

 may mention that Bacteria may often be seen developing within 

 the living cells and filaments of various Algce. In Vaucheria and 

 in Spirogyra this is commonly to be seen where the plants have 

 been kept in unnatural conditions for a time ; shut up, for instance, 

 either in a cupboard or within a stone pot. In the case of Vau- 

 cheria they may often best be recognised in and near the growing 

 points of the filaments where the microbes show themselves first 

 as mere motionless specks, which gradually develop into Bacilli, 

 and after a time take on an active existence. In the filaments 

 presenting these appearances the wall may appear quite healthy, 

 showing no signs of softening, nor is there any indication whatever 

 of the penetration of Bacteria from without. 



The same kind of thing is often to be observed within the thick- 

 walled resting spores both of Vaucheria and of Spirogyra. There 

 is the appearance of motionless particles in some part of the spore, 

 the appearance of Bacteria in the midst of these particles, and 

 the gradual assumption by the Bacteria of swarming movements. 



Again, I have frequently seen a development of motionless 

 Micrococci and Bacilh taking place inside the thick wall of a 

 Nitella cell, between it and the chlorophyll layer. Yet the normal 

 cyclosis would be still going on within this cell, showing that there 

 could be no apertures or solutions of continuity of any kind ; and 

 all the microorganisms to be seen in different stages of develop- 

 ment in this layer were quite motionless. 



I have also endeavoured to throw light upon this question by 

 repeating, with variations, some of the experiments of Lechartier 

 and Bellamy, by which they studied the fermentation that occurs in 

 various vegetables and fruits when shut up within hermetically 

 sealed vessels. They showed that the oxygen of the air was soon 

 consumed by the vegetables or fruits ; the cells of which then 

 began to break up sugar, to give off carbonic acid, and to produce 

 alcohol and acetic acid. They came to the conclusion that this 

 fermentation might certainly occur without the production of the 

 alcoholic ferment.' They, in fact, adopted Pasteur's view that the 

 formation of alcohol in these cases was due to the altered activity 

 of the cells of the fruit, which, in the absence of free oxygen, act 

 after the fashion of ferments. In a later communication,'' however, 

 these investigators stated that in their experiments with potatoes 



' " Compt. Rend.," 1872, ii., p. 1203. 

 = Loc. cit, 1874, ii., p. 1006. 



