INTRODUCTORY il 



surely, it sinks on the down-grade to the vita minima of 

 senescence, which ends in death. The contour of the curve 

 differs, of course, for different kinds of creatures, but the 

 broad fact of cyclic development remains. 



In the case of annual plants or annual animals, our 

 problem is to compare the trajectory of the life-history with 

 the curve that serves to register graphically certain big 

 physical facts of the year, notably the distribution of solar 

 energy. And when the plant or animal lives for more than 

 a year it may be for stretching cycles of years like the 

 North American Sequoias, one of which spanned the whole 

 period from the birth of Aristotle to the death of Darwin 

 we have to collate the periodicities of the year with minor 

 undulations on the main life-curve. 



THE LIVING CREATURE AND ITS SURROUNDINGS 



In its broadest statement the central problem of the 

 Biology of the Seasons is to investigate the relation between 

 the changeful organism and its changeful environment 

 within the period of the year. But this relation is manifold, 

 not simple, and it obtains in various degrees of directness. 



We do not know what life in principle is, but we may 

 describe living as action and reaction between organisms 

 and their surroundings. This is the fundamental relation 

 the absolute dependence of living creatures on appro- 

 priate surroundings. In fact, the two are inseparable. The 

 living creatures are real just in the same sense as their 

 surroundings are real, and function is but a descriptive 

 term for the dynamic relations between them. Thus we 

 cannot abstract the living creatures from their sphere of 

 essential surroundings. When we try to do this they die 

 even in our thought of them, and our biology sinks into 

 necrology. 



