354 Messrs. Pode and Lankester on the Development [June 19, 



Capsule 4 was perfectly free from organisms, and remained so during 

 a fortnight, when a fungus-mycelium made its appearance on the surface. 



Series F. Dec. 10th. — A strong infusion of turnip and cheese, pre- 

 pared as in Series B (sp. gr. 1013), was boiled in an eight-ounce flask for 

 five minutes. Three common test-tubes were superheated and placed in 

 a beaker to support them. 



No. 1. The infusion was poured in, and with it one drop of distilled 

 water. 



No. 2. The infusion was poured in and thus left. 



No. 3. The infusion was poured in and again boiled for two minutes. 



These and the flask containing the remaining infusion were left on a 

 shelf for one day; on Dec. 11, there being no cloudiness in any of the four, 

 they were placed on the top of the hot-air bath. On Dec. 13 No. 1 was 

 found to be swarming with Lejrtothrix-gYo-wiks and free Bacterium termo. 



No. 2 also was cloudy and swarmed with what Cohn calls the rosary- 

 chains. No. 3 was absolutely free from all development of life, and was 

 perfectly sweet and limpid ; so also was the fluid in the original flask, a 

 large one capable of holding eight ounces. How is the development of 

 Bacteria in No. 2 to be explained ? The original fluid remains pure ; the 

 fluid in No. 3, which was reboiled, remains so too ; the tube itself, No 2, 

 had been heated red-hot and could not be a source of contamination. 

 One's attention was therefore directed to the conditions of the passage 

 of the fluid from the flask into the tubes ; and here an explanation at 

 once offered itself. The large flask had not been superheated ; its lip was 

 still dirty, laden with Bacteria ready to contaminate fluids as they poured 

 from it ; hence the contamination of the fluid in test-tube No. 2. The 

 validity of this explanation cannot be disputed, because it is known that 

 such glass surfaces, unless specially cleansed, invariably contaminate 

 infusions exposed to them. 



Seeies G-. Feb. 11th. — The publication of Dr. Burdon Sanderson's 

 letter, describing some experiments made by Dr. Bastian, induced us 

 to make a further series of experiments with important modifications. 

 We had expressly avoided the introduction of any thing like visible lumps 

 of solid cheese or turnip into our infusions during their ebullition, 

 believing that such lumps were a possible source of the exclusion of 

 Bacteria or their germs from the killing influence of the boiling tempera- 

 ture. This precaution we had supposed (in the absence of any statement 

 to the opposite effect) to have been taken by Dr. Bastian in the experi- 

 ments adduced by him in the ' Beginnings of Life.' The presence of such 

 lumps was publicly suggested in discussion at the British-Association 

 Meeting at Liverpool as a source of fallacy, and has been demonstrated 

 to be so by Dr. Ferdinand Cohn in experiments made with peas and 

 infusion of peas (' Beitrlige zur Biologie dor Pflanzen,' Breslau, 1872). 

 Further, we had limited the bulk of our infusions and the size of our 

 experimental tubes, in view of the obvious consideration that the larger 

 the mass and area to be guarded against contamination the greater the 



