50 THEORIES OF HEREDITY AND VARIATION. 



Still another cause of variation is said to be the fact that the 

 individual is the product of two unlike parents, and consequently 

 cannot be entirely like one without causing inheritance to fail in 

 respect to the other. It cannot be denied that this is a cause, but 

 if it be the only cause, then the question would arise: How did 

 the parents become different? Those who advocate this theory to 

 the exclusion of the theory involving enviroment and use, add to 

 it the statement that the germ plasm out of which the new indi- 

 vidual grows is subject to a series of divisions and conjunctions, 

 and that as these divisions and conjunctions are not always equal, 

 the products are variable. 



ARISTOTLE ON HEREDITY. 



The earliest writer on the subject of heredity appears to have 

 been Aristotle, who lived 384 to 322 B. C. In his ''Generation of 

 Animals" (I., Sec. 35), he says: "Children resemble their parents 

 not only in congenital characters, but in those acquired later in life. 

 For cases are known where parents have been marked by scars, and 

 children have shown traces of these scars at the same points. A 

 case is also reported from Chalcedon in which a father had been 

 branded with a letter, and the same letter, somewhat blurred and 

 not sharply defined, appeared upon the arm of his child." At 

 another place (History of Animals), Aristotle refers again to this 

 matter and states that the inheritance of mutilations is rare. From 

 this it is apparent that Aristotle considered that characters acquired 

 in one generation become congenital in the next, and that he carries 

 it far enough to include the occasional transmission of mutilations. 

 Although we frequently hear of inherited mutilations, the reports 

 concerning them are hard to corroborate. Dr. Talbot 2 has, how- 

 (2) Degeneracy. 



