190 SECRETS OF EARTH AND SEA 



most plants and animals, is known to characterize certain 

 bacteria and allied Schizophyta found in hot springs. It 

 is a matter of common knowledge that many animals 

 and plants are killed by a temperature (whether too 

 high or too low for them) which allows others to flourish 

 and may be necessary for their life. Minute organisms 

 (flagellate monads) have been cultivated experimentally in 

 a nourishing liquid, the temperature of which was raised 

 daily by one or two degrees until the liquid was so hot 

 that the same species of organism was at once killed by 

 it when abruptly transferred to it from liquid at ordinary 

 summer temperature. 



The true " suspended animation " of many vegetable 

 seeds and of many kinds of bacteria under the influence 

 of cold is not an exhibition of a general property of living 

 things, but is due to a special quality of resistance gradually 

 attained by natural selection of variations a little more 

 tolerant of cold or of drought than are the majority. It is 

 of life-saving value and a cause of survival to the species 

 of plants and bacteria concerned. No doubt there is need 

 of further experiment on the subject of the " killing " or 

 destructive effect exerted by different degrees of diminu- 

 tion of temperature upon the protoplasm of all kinds of 

 organisms, and with the knowledge so obtained we shall 

 be able to frame a conception of the actual mechanical 

 and chemical peculiarities of the protoplasm of those 

 bacteria and of those vegetable seeds which can be exposed 

 to the extreme of cold for many months or for an in- 

 definite period and yet subsequently recover or live again. 

 Probably in order to survive freezing, protoplasm must be, 

 not absolutely dry, but free from all but a minimum of 

 moisture. 



