492 The Controversy on Spontaneous Generation : [Oct., 



thimbleful could be taken without containing several" germs. 

 Mr. Wanklyn's evidence certainly reads very much like that of a 

 scientific witness for the defence in a case of murder, who seeks to 

 show that the deed could not possibly have been committed upon a 

 certain clean deal floor where it is said to have been perpetrated, 

 inasmuch as he had carefully examined a square inch of the floor, 

 and had only discovered the minutest spot of blood ! 



As to the " Leptothrix " which Dr. Bastian found in turnip- 

 juice, I may mention in passing that it is considered by microscopic 

 botanists to consist of the mycelial filaments of mildew fungi,* and 

 I believe from my own investigations, to be described presently, 

 that if he had followed the growth of his " Leptothrix " he would 

 have found it to be one of those plants. Now these mildew fungi 

 are found not only in and upon decaying organic matters, but also 

 upon bare stones and rocks, where they cannot be created de novo, 

 but must necessarily result from atmospheric spores moistened by 

 showers of rain. Coupled with the two circumstances just men- 

 tioned, the account given by Dr. Angus Smith of his mode of 

 testing atmospheric air opened out to me a new field of inquiry. 

 Dr. Smith's system of washing the air is admitted to be tedious and 

 imperfect, though it may be the best in the cases with which he 

 deals ; but it seemed to me that no better method could be devised 

 for ascertaining the nature of those substances which are held in 

 suspension in the atmosphere than the one which nature provides 

 in the form of rain collected as it falls from the clouds. 



Two circumstances are well established as regards falling rain. 

 The first is that at the commencement of a shower after a long- 

 continued drought the rain brings down much more organic and 

 inorganic matter than later on ; and secondly, that after a heavy 

 shower the atmosphere is for some time comparatively free from 

 such matters. 



Then as regards the discovery of filaments in infusions, I had 

 tried some experiments with infusions of orange-juice, orange-peel, 

 apple-juice, and cabbage -juice, in distilled water, freely exposed to 

 atmospheric influences, in 1862 and 1863, and when Dr. Bastian s 

 observations were published I recollected having found such a 

 mycelium in orange-juice, and having corresponded with Professor 

 Hoffmann about it, but as he could throw no light upon the appear- 

 ance of the mycelium and I was unable to account for it, I dropped 

 the investigations. A record of these observations was however 

 kept, and was discovered by me amongst some old papers whilst I 

 was making the following experiments, and they will now be found 

 of some service. 



On the 4th of August, after a long continuance of intensely 

 hot weather, we had a violent thunderstorm. I had been expecting 



* : Micrographic Dictionary' (Yan Voorst), article " Leptotlirix." 



