256 CAUSES OF DEGENERATIVE EVOLUTION 



mission of acquired characters is, to say the least, 

 doubtful. There is no proof of individual atrophy 

 being hereditary, while with societies modification 

 may be transmitted by imitation. Institutions 

 which have fallen into disuse rarely recur in 

 freshly- formed societies. Natural selection plays 

 an all-important part in biology, but it is artificial 

 selection which almost exclusively governs the social 

 domain. 



Many vegetables, as for instance the carrot (Daucus Carota) are 

 natives of France. The seeds of the cultivated carrot must fre- 

 quently be carried to waste lands or uncultivated soil. The 

 domesticated variety, however, is never found wild although the 

 wild variety is abundant. This vegetable has lost the power of 

 struggling against weeds ; it flourishes only when it is protected 

 by man and when by repeated weedings its wild competitors are 

 removed. When it is returned to its original wild haunts the 

 plant dies out at once. 



Most cereals, although we may not know their wild ancestors, 

 are in a similar condition. For instance, if man were to cease 

 cultivating Wheat (Triticum sativum), or Rye (Secede cereale), 

 there is no doubt but that these would completely disappear. 

 Their fate would be shared in Belgium at least by many species 

 which are reaped with them at harvest, such as Centaurea cyanus 

 the Corn-flower, Agrostemma Githago the Rose-Campion, Specu- 

 alaria speculum, and others. If a corn-field were left to the free 

 operation of nature, weeds would soon intrude and cause the dis- 

 appearance of the plants usually present in it. What would 

 happen in Belgium would happen with other plants in other 

 countries. Thus, near Bergen in Norway, some plants, such as 

 Melandryum album, Silcne inflata, Vicia cracca, etc., occur only 

 in cultivated fields. In Java, many aquatic plants such as Limno- 

 cliaris Plumieri, Ludwigia perennis, Jussiaea suffruticosa, etc., 

 live only in the rice-fields which are artificially watered and 

 manured. The cessation of tillage would cause the disappearance 

 of all these plants from those localities. 



