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 
