160 DARWINISM AND HUMAN LIFE 



on the theory that the results of use and disuse and 

 of environmental change are, as such, transmissible. 

 The black skin may be interpreted as due to the 

 sun. The callosities on the knees of the wart-hog 

 may be interpreted as due to pressure on the ground. 

 The twelve hours' sleeping and waking of many 

 acacias may be interpreted as a functional adap- 

 tation which has become hereditary. But the 

 interpretations may be erroneous. 



III. Many beg the question by starting with a 

 character, like short-sightedness or gout, which 

 has not been proved to be a modification. First 

 catch your modification. The little toe is said to 

 be dwindling in consequence of wearing tight boots ; 

 but we are not sure that there is dwindling, and if 

 there is, we have no experimental reason for blaming 

 the boots. 



IV. The reappearance of a modification in suc- 

 cessive generations is often mistaken for trans- 

 mission. It may be hammered on to each suc- 

 cessive generation. Nageli put Alpine plants in 

 rich garden soil and they became very different, 

 and their progeny likewise ; but transference to 

 poor soil brought back the Alpine characters, which 

 showed that the new characters had not taken 

 any hereditary grip. 



V. Infection of the offspring by the parent before 

 birth has nothing to do with inheritance in the 

 true sense. 



VI. Transmission in unicellular organisms is not 

 to the point, for, as they have no " body," the 

 concept of somatic modifications does not apply to 

 them. 



VII. Changes in the germ-cells along with 

 changes in the body, where there are deeply 



