BACTERIA AND THEIR ALLIES 181 



In the case of the apples to which I have referred there was 

 clearly no such process of infection from within as that to which 

 Davaine refers. In the Canadian apples the change occurred 

 simultaneously in many points almost as much removed from the 

 seed cavities as from the surface of the apples ; and a comparison 

 of what was found in the primordial utricles of the cells, with what 

 has been found in similar situations in the potatoes that have been 

 referred to, leaves little room for doubt that what are shown in 

 Fig. 9, C, D, etc., are really germs of microorganisms. While in 

 the other apple delicate Fungus mycelia were found springing up 

 within various isolated cells, in the midst of the substance of the 

 fruit. 



Again, the presence of the Bacteria and other organisms within 

 the cells of the two small turnips, and the different potatoes that 

 have been referred to, are equally incapable of being accounted for 

 by any process of infection from without. There is absolutely no 

 relation between what I have found in these cases, and an actual 

 process of infection such as M. C. Potter has described (see p. 163). 

 We have to do, in fact, in the cases that I have cited, with motion- 

 less germs of microorganisms arising de novo in or on the substance 

 of the primordial utricles of isolated cells, having intact walls, and 

 scattered throughout the substance of the potatoes and the turnips 

 in question — in all parts, that is, except in the superficial portions 

 that have been saturated with the germicidal fluid in which the 

 tubers had been for a time soaked. ^ 



As I have previously pointed out (pp. 162, 173) the existence of 

 "latent germs" in the substance of healthy fruits and vegetables 

 is not assumed — it is, in fact, expressly denied. Hence the great 

 weight to be attached to the preceding observations as evidence 

 that the various microorganisms found within the cells of the fruits 

 and vegetables with which experiment has been made — like 

 those in the cells of the kidney and in the spine of the Cyclops 

 — have actually originated there by heterogenesis. 



" In these cases the organisms often have to be long and carefully searched 

 for. A perfunctory examination would almost certainly lead to the statement 

 that no organisms were present. 



