No. 543] FACTORS AND METHODS OF EVOLUTION 135 



Neither white nor black is truly swamped. The extreme 

 white or black conditions are rather rare, as is to be ex- 

 pected where a multiplicity of factors is involved. Thus, 

 if there were two (2) factors P', P" involved in the negro 

 skin then in F 2 one in sixteen should be negro-black, one 

 in sixteen pure white, and half of the remainder should 

 be light mulatto and half dark mulatto. Although studies 

 on this subject are not sufficient to warrant exact quanti- 

 tative conclusions, it is certain that more than two and 

 probably more than three factors are involved in the 

 pigmentation of the negro. If a number of mulattoes 

 inhabited (as sole occupants) an oceanic island, and bri'd 

 there, in the course of generations both the white and tin- 

 black types of skin color would be found again—the two 

 extreme types are not swamped. Consequently from our 

 present point of view, isolation is much less essential 

 than was formerly thought to be the case. Practically 

 important as it may be to keep races pure and ensure the 

 absence of intergrades or hybrids, it is not essential to 

 the survival of new traits that have arisen in the midst 

 of the old stock. 



Fifth, the experimental study of heredity has thrown 

 light upon the question of the origin of new determiners. 

 Every critical experiment that has been tried demon- 

 strates again that the somatic condition exercises little 

 or no influence upon the determiners in the germ-plasm 

 The first crucial experiment on this subject of which 1 

 know was that of Francis Galton, who infused into sil- 

 ver-gray" does the blood of either yellow, black and 

 vfhite, or common agouti rabbits. In one case an angora 

 buck and yellow doe had their carotid arteries so con- 

 nected that for over half an hour the blood of each 

 flowed into the body of the other; so that about one nail 

 of the blood of each was alienized. Yet, when the ra - 

 bits that had been operated upon were used as paren ^s, 

 the offspring indicated that their gen 

 gone no modification m consequence of 

 Recently the question has been revived by Guthi 



of tin 



