INTRODUCTION 17 



with already existing forms, and from the biological 

 point of view should be regarded rather as sugges- 

 tive and tentative than as dogmatically claiming 

 citizenship with microbes of other kinds. 



There is, as we think, strong evidence that they may 

 be some elementary bacilli. The limits of temperature 

 are very different from those of ordinary microbes. 

 Probably none with such optimum temperature would 

 ever have survived. The radiobe is soluble in warm 

 water, and ordinary bacteria are likewise soluble at 

 temperatures exceeding boiling point. Primitive 

 forms of life may have been able to exist only at very 

 low temperatures. They may have originated at the 

 bottom of the sea, where the temperature is very 

 low. The suggestion that they did so arise has often 

 been proposed, and it seems in the light of these 

 experiments that the idea is not at all impossible. 

 At these temperatures such bodies would not neces- 

 sarily be soluble. 



But, granting the fact of solubility in water at 

 temperatures somewhat higher than ordinary temper- 

 atures to be totally distinct from the dissolution of 

 cells at comparatively high temperatures such as 

 boiling point, what reason is there to suppose that 

 such primitive forms of life if they could be obtained 

 some day, supposing that they have not yet been 

 found, should be insoluble at any particular temper- 

 atures ? Such elementary types would doubtless not 

 possess all the properties of the more highly organised 

 types with which we are now familiar, and there is 



c 



