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THE AMERICAN KATUEALIST [Vol. L VI 



since it" can be, in fact is, contributed in reproduction al- 

 most wholly by one parent, tlie female. It is apparently 

 a medium which responds specifically to the action of 

 the respective chromosomal incitants, whether these be of 

 maternal or paternal origin. All geneticists agree to-dayj 

 I think, that any character of an adult can not be merely 

 the outcome of a unitary germinal antecedent; it is the 

 product of many factors. And ordinarily what we see as 

 a character-difference is probably merely the outcome of 

 a factor-difference in one of the chromosomal cooperants. 



In conclusion, let me say first of all that no one more 

 than niyself realizes the inadequacy of my present argu- 

 ment as a complete or satisfying theory. The knowledge 

 in the fields on which it is based is as yet far too frag- 

 mentary to warrant anything but tentative conclusions. 

 But since various facts seem to me to point toward the 

 view that certain types of immunological reactions, no- 

 tably the cytolytic, engendered against various somatic 

 constituents may occasionally also affect chemically re- 

 lated substances in the germ, and inasmuch as many 

 other facts lend themselves to such an interpretation 

 without undue violence to scientific credulity, I have felt 

 justified in presenting the whole matter in the form of a 

 working hypothesis. 



In the short time remaining I can not enter into the 

 important question of whether or not changes induced in 

 the blood-serum might be instrumental in leading to pro- 

 gressive rather than regressive evolution, and even had 

 I time for such a discussion, there are not sufficient data 

 available to support such a discussion affirmatively. I 

 should like merely to point out in closing that through 

 exercise we can initiate and promote growth in various 

 parts of the soma, we can induce hypertrophy, and in so 

 doing we are in some way leading the protein and other 

 constituents of the cells in question to make more of their 

 own kind of substance, in other words, to reproduce their 

 kind. We do not know what stimulates them to do so, 

 but, in part, it may well be something that is or can be 

 transported in the circulating fluids of the body; and if 

 so, then there exists the possibility that the correspond- 

 ing germinal representative of such a part, however 

 tenuous the thread of chemical connection, might also be 

 modified in the direction of progressive germinal change. 



