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, 1878. 
Dr. Willi A.M Roberts exhibited some preparations and 
experiments 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 ; the 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 off above the cotton w r ool, so 
as to permit free ingress and egress of air. 
