THE WONDER OF LIFE 483 



occurred, though microscopic examination would show 

 that some of the cells were alive. But how much more 

 difficult the question becomes when we pass to dried up 

 paste-eels, small thread- worms or Nematodes of the family 

 Anguillulidse, which can remain dry and brittle for as 

 long as fourteen years, and yet become lively again when 

 restored to water ! What is life in these inert threads, 

 which exhibit no sign of living ? What has happened in 

 the fifteenth year, when although no visible change has 

 occurred, the threads are no longer susceptible to the 

 reviving influence of water ? They are dead ; but what 

 has happened ? 



Latent Life. The familiar sight of bags of dry seeds 

 in the seedsman's shop raises many questions. In what 

 state is the life of these seeds for it is to be hoped that 

 most of them are still alive ? Can they remain alive 

 without actually living ? Vital processes involve chemical 

 change (metabolism) : has metabolism come to a stand- 

 still or is it going on very slowly ? It is not so easy to test 

 this as might be imagined, for the fire of life may be kept 

 burning so very, very low that no change is detectable in 

 the surrounding medium. Some plants can respire without 

 taking in oxygen from outside, and some others, e.g. 

 succulents, can respire without giving out any carbon 

 dioxide. Of course if the protoplasm is actually living it 

 is transforming energy, and if it has no income it must be 

 living on its own resources, therefore the life of seeds must 

 be limited. We know securely from Becquerel's careful 

 testing that seeds may germinate after resting for eighty- 

 seven years in a herbarium a hortus siccus indeed. 



Becquerel has made important experiments on the 

 latent life of dry seeds. He showed, for instance, that the 



