PROCESS OF REPRODUCTION IN ORGANISMS. 37 



characteristic of the organism and in the colloid field in which 

 these processes occur. It seems to me no more necessary to 

 postulate a specific hereditary entity for a specific morpho- 

 logical character of an organism than it is to postulate such 

 an entity for a sand bar or an island developing in a river. 



In a recent paper (Child, 'lie) I suggested a definition of 

 heredity which I repeat here since it seems to cover the ground 

 and does not involve unwarranted assumptions. "Heredity 

 is the sum total of the inherent capacities or "potences" with which 

 a reproductive element of any kind, natural or artificial, sexual 

 or asexual, giving rise to a whole or a part, enters upon the develop- 

 mental process." In short the heredity of any reproductive 

 element is simply the record in its capacities of its past history. 

 Such a statement does not, however, imply that every factor 

 in its past has left a permanent record. If we admit that the 

 sex cells, like the asexual reproductive elements and the re- 

 productive elements resulting from the artificial isolation of 

 pieces by operation, are at some stage of their development 

 integral physiological parts of the organism then we may define 

 heredity as the capacity of a physiologically or physically isolated 

 part for regulation. 



In the realization of these capacities and potentialities environ- 

 mental factors, internal and external, play an important part. 

 A "latent" character is simply non-existent as an entity, i. e., 

 it exists only in the potentialities of the system. Latent char- 

 acters are no more real things than are latent sand bars and 

 islands in a river. The organism possesses almost infinite 

 potentialities, but what conceivable reason is there for regarding 

 them as different from potentialities elsewhere in nature. 

 HULL ZOOLOGICAL LABORATORY, 

 UNIVERSITY OF CHICAGO. 



REFERENCES. 



Boveri, Th. 



'10 Die Potenzen der Ascaris-Blastomeren bei abgeiinderter Furchung. Fest- 

 schr. zum sechzigsten Geburtstag Richard Hertwigs, Bd. III., 1910. 



Braem, F. 



'08 Die Knospung der Margeliden, ein Bindeglied zwischen geschlechtlicher 

 und ungeschlechtlicher Fortpflanzung. Biol. Centralbl., XXVIII. Bd., 

 1908. 



