83 The Mechanism of Evolution in Leptinotarsa 



activities of greater or less magnitude between the parental gametic systems, 

 and represented by integrated substance of specific composition, with specific 

 capacity of reaction when combined with some one or more complementary 

 agents in its new position. 



The most striking fact in this metathetic reaction is that the agent always 

 goes over to a precisely similar position, mode, and time of somatic expression, 

 or, in other words, it goes to a basal point of attachment in the new gamete, 

 where it finds or establishes physical relationships that hold it firmly in position 

 and in whole or in part govern its reactions in the development of the zygote 

 which it may help to form. 



Another striking fact of these reactions is the uniform finding that the 

 metathetic reaction is always between qualities having the same general type of 

 manifestation, as interchange of color, of form, of pattern or symmetry, and so 

 on, and never is there interchange of a color character with one of form, food- 

 relations, or reproductive activity, so that we are coming to see that there are 

 groups of these agents and of their associations, and that the Mendelian reac- 

 tion is between differences in these groups, and not between different groups. 



A second point that has been forced upon my attention is that it is the deter- 

 mining agents, the determiners, that are chiefly, if not exclusively, concerned 

 in this metathetic reaction, while the compliment or factor in my materials 

 never shows this type of reaction. Further, the factor is in my experience 

 always associated with the basal species complex, firmly bound into one associa- 

 tion, productive of the basal species complex. What these are in the composi- 

 tion of the gametic material no one knows, but their reactions, as I have 

 observed them, suggest that they are possibly different colloids in the general 

 colloidal mixture that forms the ground-substance of the living mass, and of 

 this interpretation support is found in the fact that in my materials these factors 

 are properties of the whole mass, and so strongly suggest a general distribution 

 throughout the entire germinal material. 



The determiners, on the other hand, are numerous, and are the agents that 

 show not only metathesis, but also capacity for fragmentation, groups of them 

 being dissociated in one case or lesser groups in another, and in this class of 

 agents many interchanges, from extensive on the one hand to increasingly 

 minute on the other, have been possible in my materials. 



These agents do not behave as properties of the whole mass, but in relation 

 to specific portions, locations, in time, in ontogeny, and in relation to specific 

 activities, and appear to be associated with basal material points of attachment 

 that are specific for the source from which the gametic material came. These 

 latter seem not to be dissociated from the original mass in the usual metathetic 

 reactions, but to maintain their association with the species complex, inter- 

 changing only the specific portions that are productive of localized determinative 

 actions. 



These experiences with my materials, and the data that has come from the 

 investigations of the neo-Mendelians, lead directly into the problems of the 

 architecture of the germinal material. 



