52 



I trust that at some future time I shall be able to render 

 a more satisfactory account of this interesting substance, 

 and particularly of its formation. 



Macclesfield, January, 1873. 



Dr. Willi A.M Roberts exhibited some preparations and 

 experhnents bearing on the question of biogenesis. He 

 stated that in the last two and half years he had performed 

 over 300 experiments. His results supported the conclusion 

 that the fungi, monads, and bacteria which make their 

 appearance in boiled organic mixtures are not due to spon- 

 taneous evolution, but arise exclusively under the influence 

 of pre-existing germs or ferments introduced from without. 

 His method of experimenting consisted chiefly in exposing 

 organic solutions and mixtures to a boiling heat in glass 

 flasks whose necks had been previously tightly plugged 

 with cotton wool. Two modifications of the experiment 

 were adopted. 



I. In the first modification a 4-ounce flask was employed, 

 and the heat applied directly by means of a gas flame. 



II. In the second modification — after the introduction of 

 the materials to be operated on — the elongated neck of the 

 flask was sealed hermetically by the blowpipe above the 

 plug of cotton wool ; tlie flask was then weighted with a 

 collar of lead and immersed in a large can of water ; the 

 can was then put on the fire and the water boiled for 20 or 

 30 minutes. During the process of boiling the flask was 

 maintained in an upright or semi-upright position, in order 

 to prevent any wetting of the cotton- wool plug by the con- 

 tents of the flask. When the can was cold the flask was 

 removed and its neck filed oflf above the cotton wool, so 

 as to permit free ingress and egress of air. 



