16 BIOLOGY 



One cannot be too strongly warned against expecting 

 that these criteria can be applied successfully at first, 

 for there are certain stages in the life of the living 

 organism when all the life processes seem not to exist. 

 This passive state found alike in plants and animals 

 may be considered as a state in which the living organism 

 becomes capable of withstanding conditions unfavour- 

 able to activity. We find, for example, that seeds may 

 lie dormant for a long period of years, and that some 

 animals may lie in this dormant condition for periods 

 up to fourteen years. There is nothing to distinguish 

 the substance of the living organisms under these con- 

 ditions from non-living substance, but still we find that 

 when introduced into favourable conditions, they 

 germinate or again begin an active life. This latency 

 of life is well shown by seeds which have been found 

 in the graves of mummies and also in the case of paste- 

 eels. It seems certain that certain conditions such as 

 cold, dryness or failure in the food-supply, tend to 

 induce the passive state, while warmth, presence of 

 moisture, and a suitable food-supply are factors in 

 restoring the active state. 



CHAPTER III 



THE CELL 



EVERY living organism consists of a single unit of living 

 matter, a cell, or of an aggregate of these units arranged 

 in many and diverse ways. At first it was supposed 

 that every unit exhibited more or less uniformity of 



