52 UVli : OUTLINKS OF GENERAL BIOLOGY 



(i) functional deix?ndence, 



(2) jx^riixlic attuncment, 



( ^) reactions and adjustments, 



(4) lasting mcKlifications, 



(5) inllucncing the vigour of the germ-cells, 

 (()) provoking variations in the germ-cells, 



(7) bringing about sifting and again initiative. 



We have given a more detailed analysis in Evolution (Home 

 Tniversity Library), 191 1. 



THE MARCH OF THE SEASONS 



One of the largest facts of life is its waxing and waning as the earth 

 moves round the sun. This is the subject of the science of Phenology 



-an inciuiry that comes home to us in temperate countries, where 

 the seasons are clearly j)vmctuated, and do in no small measure hold 

 living creatures in their grip. 



As the sun is the source of almost all the energies of the earth, 

 our income of heat and light in i)articular- varies with our 

 seasonal position in regard to the centre of our system. The basal 

 fact is that the ratio of the heat supply in summer to that in winter 

 is 63 : 37 in our latitudes. 



IVginning with sjiring, we see it as tlie season of renewed activity 

 and strengtli. The water in the soil begins to move again, and there 

 is a (piickening of the cycle of mist and cloud and rain. Into the 

 quiescent seeds the water begins to soak, sharing in the fermenting 

 that is going on; the seeds sprout, the .seedlings lift their heads 

 above ground, the brown earth becomes green. The water ri.ses to 

 the tops of the tall trees, and the buds that were formed in the 

 warmth of last simimer's sunshine begin to grow and swell and 

 ojxMi. scattering the protective bud-scales on the ground. Almost 

 everywhere over the earth there is stretched the green veil which 

 enables the plants to capture part of the i)ower of the sunshine. 

 Spring is a time of fresh life, of reinvigoration, of becoming young 

 again. 



riie "winter-slee|Hrs,'" like hedgehog and dormouse, come out 

 of thrir retreat^, with a new lease of life after their long rest. Spring 

 is a time of nawakcning. The migratory birds, like swallow and 

 swift, cuckoo and nightingale, begin to return from their winter 

 • piarters in the south, and some of them aie no sooner here than 

 they l)egin to sing songs of love. For spring is a time of love-making. 

 Naturally enough it is also a time of young things, for eggs are laid 

 anrl new creatures are born. Who can think of spring without 

 picturing caterpillars and tadpoles, nestlings and lambs? The ponds 



