112 DARWINISM • chap. 



species found in the same area. So, each part of the 

 world has its own peculiar forms of pines, firs, and cedars, 

 hut the closely allied species or varieties are in almost 

 every case inhabitants of distinct areas. Examples are the 

 deodar of the Himalayas, the cedar of Lebanon, and that of 

 North Africa, all very closely allied but confined to distinct 

 areas ; and the numerous closely allied species of true pine 

 (genus Pinus), which almost always inhabit different countries 

 or occupy different stations. We 'will now consider some 

 other modes in which natural selection will act, to adapt 

 organisms to changed conditions. 



Adaptation to Conditions at Various Periods of Life. 



It is found, that, in domestic animals and cultivated plants, 

 variations occiurring at any one period of life reappear in the 

 offspring at the same period, and can be perpetuated and 

 increased by selection Avithout modifying other parts of the 

 organisation. Thus, variations in the caterpillar or the cocoon 

 of the silkworm, in the eggs of poultry, and in the seeds 

 or young shoots of many culinary vegetables, have been 

 accumulated till those parts have become greatly modified and, 

 for man's piu"poses, improved. O^ving to this fact it is easy 

 for organisms to become so modified as to avoid dangers that 

 occur at any one period of life. Thus it is that so many 

 seeds have become adapted to various modes of dissemination 

 or protection. Some are "SAanged, or have down or hairs 

 attached to them, so as to enable them to be carried long 

 distances in the air ; others have curious hooks and prickles, 

 which cause them to be attached firmly to the fur of mammals 

 or the feathers of birds ; while others are buried within sweet 

 or juicy and brightly coloured fruits, which are seen and 

 devom-ed by birds, the hard smooth seeds passing through 

 their bodies in a fit state for germination. In the struggle 

 for existence it must benefit a plant to have increased means 

 of dispersing its seeds, and of thus having young plants pro- 

 duced in a greater variety of soils, aspects, and surroundings, 

 Avith a greater chance of some of them escaping their numerous 

 enemies and arriving at maturity. The various differences 

 referred to Avould, therefore, be brought about by variation and 

 sur\dval of the fittest, just as siurely as the length and quality 



