Problems of Gametic Constitution 77 



produce desired combinations and results that are well within the expectancy 

 of error, thus showing that the metliod has at least some present value in 

 determining the nature of this substance, its factors of composition, its struc- 

 ture, and exact mode of action in specific combinations. 



The conception of exact conditioning agents in the germ-plasm, so logically 

 and philosophically developed in Weismann's writings, and the proof of these 

 that came through the advances made after the recovery of the investigations 

 of Mendel by the neo-Mendelian investigators, does not leave any doubt of the 

 existence in the germ-plasm of agents of diverse potentialities, whose presence 

 is necessary for the production of specific end-results in the soma. 



The investigations of the neo-Mendelians show in an incontrovertible manner 

 that there are gametic agents whose action can be predicted with entire mathe- 

 matical accuracy ; but it has been asserted that these agents concern only super- 

 ficial and unimportant characteristics in the organisms investigated, and that 

 there is a basis that is not at all dissociated to which these agents are attached 

 as more or less unimportant additions. 



It is undeniably true that the great majority of the characters of any one 

 parent entering into a mating not only retain their identity, but also their asso- 

 ciation with the total complex of characteristics that came from that parent, and 

 that only one or at most only a few are lost or transferred or replaced as the 

 result of the crossing. There is a retention of the specific parental gametic 

 complex of the species. Does this indicate a different material basis, or only 

 the retention of the integrity of composition and structure of the system, with 

 capacity to act for a time in union with some other system, but no ability to enter 

 into a permanent union therewith ? 



In the crossing of natural species it has been my experience that the species 

 base retains its integrity with exactness, but with varying degrees from complete 

 integrity, giving only exact and typical monohybrid reactions and the extraction 

 of pure parent types in Fj through series in which one or two or a few char- 

 acteristics were interchanged, giving new synthetic extracted types in subse- 

 quent generations to complex cases in which there was much interchange, and 

 lastly to most intricate examples in which as far as could be determined new 

 and permanent combination had been made between the two uniting gametes, 

 with loss of many portions of the two parental systems, giving rise to new com- 

 binations that were, as far as could be determined, permanent in character and 

 action. In these series of experiences, details of which are given in the chapters 

 that follow, I have not been able to draw any Hne of demarcation, on one side 

 of which is the species base and on the other the superficial gametic agents that 

 are capable of interchange or loss. As far as my experiences go, it seems the 

 most logical concept that if the factorial working of these basic phenomena of 

 organisms are true in part they are also true in all characteristics of the organ- 

 ism, and that the germ-plasm must be thought of as a physical system witli 

 exact composition and structure, precisely as in the non-living materials of the 

 planet, with differing degrees of capacity for dissociation and metathesis of 

 factors. This capacity for dissociation and metathesis is not alone due to the 

 nature of the specific form, but also to the reactions and the conditions of 

 reaction to which the complex is subjected. That is, in one set of reactions 

 under one set of conditions, there may be complete retention of integrity, as in 



