82 FOOT-NOTES TO EVOLUTION. 



can never be forgotten. With bird or mammal the ac- 

 celeration is still more marked, and the gill structure 

 has passed into atrophy before the egg is hatched or the 

 animal born. The force of acceleration hurries the em- 

 bryo along through these temporary stages, and with 

 this shortening of useless steps comes the possibility of 

 higher development. 



Conversely retarded development brings about de- 

 generation, while variations in any direction with species 

 or organs has the larger purpose of increasing variety, 

 of promoting individuality. 



Similar results are brought about by variations in 

 use or in effort. The organ which is used thrives, while 

 the unused organ disappears with its function. These 

 changes affect the individual vitally and directly. 

 Whether they are transmitted from generation to gen- 

 eration in any degree is still unknown. Characters re- 

 sulting from the use, effort, or experience of the indi- 

 vidual are known as acquired characters. Such acquired 

 characters are the strong arm of the blacksmith, the 

 skilled hand of the artist, the trained ear of the musi- 

 cian. These characters are not subject to inheritance 

 by the laws of heredity in the same way or in the same 

 degree that inborn characters are. Nevertheless, it is 

 claimed by a large number of evolutionists, the so-called 

 Neo-Lamarckian school, that there is a law of the trans- 

 mission of acquired characters. Such a law was formu- 

 lated by Lamarck as his fourth law of evolution in these 

 words : 



"All that has been acquired, begun, or changed in 

 the structure of individuals in their lifetime is pre- 

 served in reproduction and transmitted to the new in- 

 dividuals which spring from those who have inherited 

 the change." 



In the words of Herbert Spencer, the leader of the 



