DR. W. ROBERTS ON BIOGENESIS. 
475 
By carrying the experiments a step further it was shown that, although the contents 
of the flasks had not acquired the power to germinate, they had acquired the property 
of enabling freshly introduced germs to survive a boiling heat ; for when the flasks 
were unplugged and infected with ordinary air or water and then replugged and boiled 
five minutes, their contents in every instance germinated in a few days. 
These experiments appear to warrant the following conclusions : — 
1. That the germinal particles of air and water (or some of them) are capable of 
surviving the heat of boiling water in certain media. 
2. That when we speak of different liquids and mixtures as possessing different 
degrees of resistance to sterilization by heat, it would be more exact to say that the 
germinal particles of air and water possess varying degrees of vital resistance to heat 
according to the nature of the media in which they subsist. 
The issue of the foregoing inquiry has been to confirm in the fullest manner the 
main propositions of the panspermic theory, and to establish the conclusion that 
Bacteria and Torulce, when they do not proceed from visible parents like themselves, 
originate from invisible germs floating in the surrounding aerial and aqueous media. 
Nevertheless I cannot withstand the impression that this general and common mode 
of origin may, under rare conditions, be supplemented by another and an abiogenic 
mode of origin. 
The facts on which this impression rests are only isolated and quasi-exceptional 
units among countervailing hundreds ; but the record of this inquiry would be incom- 
plete without an account of them. 
The facts alluded to consist, first, of cases of retarded germination of Bacteria ; and, 
secondly, of two cases in which fungoid vegetation, of a type new to me, appeared in 
plugged bulbs after being heated in boiling water. 
In studying the sterilization of organic liquids by heat, I found, as a rule (as already 
stated), that if germination did not take place within four days it did not take place at 
all ; that is, the media proved to be permanently sterilized. But occasional exceptions 
to this rule were encountered, in which the media remained sterile for six* eight, and, 
very rarely, for ten and twelve days, and then germinated. The most remarkable of 
these exceptions were, however, the two following : — 
1. November 21, 1871. — Some dried marrow-fat peas were soaked in water for thirty 
hours, until they had fully recovered their original plumpness. About a dozen of 
these were enclosed, with water, in a plugged flask and boiled over the flame for ten 
minutes. A second flask was charged and boiled in the same way, except that the 
strong, and afterwards diluted down with water to the standard density of 10D6. But on several occasions I 
was obliged to boil the infusions before diluting and alkalizing, in order to keep them sweet until my engage- 
ments permitted me to go on with the further steps of the experiments. In these instances the resistance to 
sterilization was just as great as when there was no preliminary boiling. 
