THEORIES OF HEREDITY 73 



(c) Particulate Inheritance. 



It has been indicated above that the determinants of any 

 given species are representative of all the racial characters 

 of that species, but we added that this is the case only for 

 the determinants of a majority of Ids. In fact, not all the 

 Ids contain determinants representative of all the characters 

 of the species. In other words, the process described already 

 under Maturation, showing that the Idants and Ids of the 

 germ-plasm become individually different from each other, 

 goes still farther, and applies to a certain extent also to the 

 determinants. A certain change in the determinants of 

 the Ids takes place, so that not all the Ids contain exactly 

 the same kind of determinants. This is due to the pro- 

 gressive evolution of the species, by means of which the 

 species varies, and gradually alters its characteristics in 

 the course of time. Corresponding with the appearance 

 of new characters in a species, the determinants of the 

 species will be altered (indeed, the change of the deter- 

 minant precedes that of the part expressed by it), the 

 change appearing first in a few Ids, then in more, until, 

 when a new character is firmly established, it will be 

 represented by the determinants in most of the Ids of the 

 germ- plasm. A minority of determinants may still exist, 

 representative either of the past stages or of new incipient 

 stages of the species. We have thus in the germ-plasm of 

 any species two kinds of determinants the majority, being 

 homodynamous, representing characters of the species well 

 established, and a minority of determinants, representa- 

 tive of characters in all stages of transition, which, there- 

 fore, in their action would be heterodynamous. 



Now, the number and strength of the homodynamous 

 and heterodynamous determinants may be different for 

 the various parts of the organism, and may vary differently 

 in the germ-plasm of the father and mother species. If, 

 then, during the development of the individual each time 

 a different set of determinants becomes predominant at a 



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