MELANIN COLOR FORMATION. 317 



presence or absence (dominance, inhibition, contamination, etc., 

 made use of by some workers) of particular factors in the gamete, 

 But facts at hand, despite an opposite contention, will go very 

 far towards showing that the method of analysis of the Men- 

 delian worker has not permitted him to decide the question as to 

 the real number and scparateness of the factors ; nor yet to de- 

 termine as to whether certain of the factors were at all repre- 

 sented in the germ cells, or whether they may not have arisen 

 during the ontogeny as a direct result of tissue differentiations, 

 through regulatory processes, or otherwise, and quite indepen- 

 dently of the existence of a definite determiner in the gamete or 

 germ cells. 



As Mendelism has developed, it has lent support to the doc- 

 trines of preformation, unit characters, and discontinuous varia- 

 tion. The facts and interpretations here brought forward disclose, 

 on the other hand, no small amount of epigenesis, and strongly 

 support the proposition that present and new knowledge will 

 lessen, not widen, the apparent gap between discontinuous and 

 continuous variability. There is, too, at present a marked tend- 

 ency in some quarters to further elaborate and extend the 

 " factor " hypothesis, which furnishes an additional and specific 

 reason for my calling attention to some facts from my province 

 of study which indicate that already we have represented too many 

 factors in the germ cells ; that qnite certainly some factors which 

 have by Mendelian interpretation been made to circulate through 

 the germ cells are never represented (in the Mendelian sense) in 

 these cells at all ; and finally that many factors considered most 

 separate and discreet by Mendelians, can now be proved to be 

 but points in lines of perfect continuity. 



It will no doubt be urged by some Mendelians that the obser- 

 vations recorded here are quite wide of the mark because the 

 writer has no experience in animal breeding. It is very true that 

 I have not personally carried through any breeding experiments 

 whatever. For information in this field I have depended upon 

 what I have been able to see of the breeding and hybridization 

 experiments conducted by others, and upon the literature of the 

 subject. My own work for several years has been largely in the 

 field of developmental and color physiology ; its aim being to get 



