42 INHERITANCE, VARIATION AND SELECTION. 



between males for the possession of females, and inability to escape 

 from enemies. During a period of drought when there is a scarcity 

 of herbage, the giraffe with the longest neck will be able to obtain 

 the best supply of food and will survive when the shorter necked 

 individual will succumb from starvation. When deers are pursued 

 by wolves, it is the fleet ones that will escape and the slow ones 

 that will fall victims. Among polygamous animals, as wild horses, 

 wild cattle, the deer family and elephants, the larger and stronger 

 males expel or kill the smaller and weaker ones. This process of 

 elimination of the weaker or less perfect, and preservation of the 

 stronger and best adapted has been called natural selection, or the 

 survival of the fittest. 



In addition to the forms of selection described, there is another 

 form called sexual selection, a term used to express the process by 

 which a female selects and accepts the attentions of the male which 

 is most pleasing to her. It is through sexual selection that many 

 male birds have obtained their gorgeous plumage and other birds 

 have acquired the power of song. 



It will be evident that before there can be selection, or survival 

 of the fittest, there must be variations from which the selection is 

 made, and that to make such selection effective there must be the 

 force of heredity to preserve the variations selected. Having these 

 two forces, selection becomes an explanation of the process of 

 evolution. 



It is to Mr. Darwin that we owe our knowledge of the existence 

 of natural selection and its action upon all forms of animals and 

 plants. He considered it as probably the most potent factor in 

 organic evolution, but since his day many naturalists have come to 

 consider it the only factor. 



