Eeactions and Peoducts in Interspecific Crosses 145 



to the larval color and the meristic pattern system of the larvae, permit of inter- 

 change or metathesis of these groups between the separating systems of the 

 groups of agents that are productive of the characters in question, and these 

 interchanges seem to be equal in both directions. How this is produced or 

 what it is that passes between the two systems is unknown, but it is clear that 

 something does pass from one to the other system ; that there is true metathetic 

 change between the two interaction masses that represent the germinal sub- 

 stance derived from each parent and which are separating from the combina- 

 tion of them into masses pure for the substance contained therein, with the 

 exception of such additions or removals as may have been produced by the 

 metathesis resulting from the interaction of the two gametic masses. On the 

 surface it appears much like some type of mass-reaction, accompanied by inter- 

 change between the two interacting masses. These interspecific crosses show 

 that the mass of the gametic system, acting as a whole, as an indivisible unit 

 of reaction in one combination, in another allows of interchanges in parts of 

 its system, resulting in new pure breeding combinations. 



These results raise the question whether the changes found are the extent of 

 possible change, or whether there is a specific residue which may or may not be 

 incapable of dissociation and recombination. Bateson and others have in some 

 measure pictured the conditions as the combination of a basal portion upon 

 which is placed or attached the agents capable of being changed in position and 

 recombined. This basal portion is simply the unknown unanalyzed residue of 

 the gametic complex, and there is no reason to expect a specific indivisible base 

 upon which to build, and if the principle of factorial constitution and operation 

 is true in part it seems most probable that the same condition holds throughout ; 

 at least that is the condition that one finds in unorganized substance, and is, no 

 doubt, true for all substance. 



