198 EVOLUTION AND ANIMAL LIFE 



Lamarck or even that of Darwin or Spencer. The characters 

 shown by any adult individual are all in a sense acquired char- 

 acters, their development dependent largely on nutrition and on 

 the influences of environment. The facts of heredity show that 

 it is not the actual traits of the parents, but rather their poten- 

 tialities which are inherited. Moreover, acquired characters 

 are simply matters of degree of development. They represent 

 in no case anything qualitatively new. Taking the modern 

 theories of heredity, it is perhaps not conceivable that "all that 

 is acquired, begun, or changed" in the physical or mental life 

 of the individual should produce a corresponding change in the 

 germ cells, or in the cells from w y hich these are thrown off. 



On the other hand, Dr. Weismann has admitted the possi- 

 bility that one-celled animals and animals of simple structure 

 in which the germ cell shares in the general relation of the body 

 cells to the environment may be effected by developmental con- 

 ditions. In other words, the inheritance of acquired characters 

 may be a reality in the development of Protozoa, the simpler 

 Metazoa, and the lower types of plants, but this condition does 

 not obtain among the higher forms. 



In much of the discussion on this subject the term "ac- 

 quired characters " is used with an uncertain or double meaning. 

 The term should be limited to traits of the individual which 

 were not inborn or blastogenic, and would not be exhibited in 

 the natural or usual development of the individual. In general, 

 such traits would arise either from the operation of use or disuse 

 of parts, or other functional stimulation derived from the en- 

 vironment. 



An illustration of an acquired character resulting from use 

 and disuse would be the increased size of the arm in the black- 

 smith, or the decreased leg muscles of the tailor. The training 

 of a musician or of a mathematician would give increased power 

 along the lines of the training. The neglect of the musical or of 

 mathematical ability would lead to the relative mediocrity of 

 this form of ability. Education in a general way increases mental 

 capacity: neglect of education allows it to become relatively 

 less. The supposed inheritance of results of civilization forms 

 an important part of the philosophy of Herbert Spencer. Is 

 civilization the inheritance of the power gained by past suc- 

 cesses, or is it simply the acquisition of the machinery which 

 past successes have produced? As to this Herbert Spencer 



