ABIOGENESIS. 39 



many of them naturally pass a considerable part of their ex- 

 istence in a condition in which the}' show no marks of life 

 whatever save growth and multiplication. 



If indeed it could be proved that, in cases which are not 

 open to doubt, living matter is always and invariably killed 

 at precisely the same temperature, there might be some 

 ground for the assumption that, in those which are obscure, 

 death must take place under the same circumstances. But 

 what are the facts ? It has already been pointed out that, 

 leaving Bacteria aside, the range of higli temperatures be- 

 tween the lowest, at which some living things are certainly 

 killed, and the highest, at which others certainly live, is rather 

 more than 100° Falir., that is to say, between 104° Fahr. and 

 208° Fahr. It makes no sort of difference to the argument 

 how living beings have come to be able to bear such a tem- 

 perature as the last mentioned ; the fact that they do so is 

 sufficient to prove that, under certain conditions, such a tem- 

 perature is not sufficient to destroy life.^ 



Thus it appears that there is no ground for the assumption 

 that all living matter is killed at some given temperature be- 

 tween 104° and 208° Fahr. 



No experimental evidence that a liquid may be heated to 

 n degrees, and yet subsequently give rise to living organisms, 

 is of the sm illest value as proof that abiogenesis has taken 

 place, and for two reasons : Firstly, there is no proof that 

 organisms of the kind in question are dead, except their per- 

 manent incapacity to grow and reproduce their kind ; and, 

 secondly, since we know that conditions may largely modify 

 the power of resistance of such organisms to heat, it is far 

 more probable that such conditions existed in the experiment 

 in question, than that the organisms were generated afresh 

 out of dead matter. 



Not only is the kind of evidence adduced in favor of 

 abiogenesis logically insufficient to furnish proof of its occur- 

 rence, but it may be stated, as a well-based induction, that 

 the more careful the investigator, and the more complete his 

 mastery over the endless practical difficulties which surround 

 experimentation on this subject, the more certain are his ex- 

 periments to give a negative result ; while positive results 

 are no less sure to crown the efforts of the clumsy and the 

 careless. 



1 Messrs, Dallinger and Drysdale have recentl.y shown good grounds for 

 believing that the o;erms of some Monads are not destroyed by exposure to a 

 temperature of 260° Fahr. or even 300° Fahr. 



