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THE AMERICAN NATURALIST. [Vol. XXXVIII. 



both intermediate forms like the hybrids of the second generation and 

 forms which have reverted to the brown grandparent, as the white 

 doves have seemingly returned to the white grandparent." Here we 

 have a clear recognition of what Mendel calls dominance ! Also, this, 

 (p. 48) : "If a spermatozoon and an egg containing characteristics 

 of the same species unite, then the reversion will be to that of the 

 species ; if a sperm cell containing the characteristics of one species 

 happens to unite with an ovum containing characteristics of the other 

 species, then the offspring will be of the mixed type again. By the 

 law of probability the latter will be the more prevalent occurrence, 

 because there are four combinations possible, and two of the four 

 would result in the production of mixed offspring, w^hile only one 

 combination could result in a return to one of the ancestral species." 

 Here we have even the quantitative part of Mendel's law expressed in 



The foregoing Mendelian generalizations are suggested by the 

 behavior of the hybrid germ cells in the spermatogenic stages. The 

 mitoses are frequently abnormal — two spindles lying side by side, 

 owing to the fact that the chromosomes are segregated in different 

 parts of the cell. This segregation suggests an incompatibility 



"pure " germ cells — with the parental qualities segregated. 



Finally, the all too brief chapter of suggestions will repay careful 

 study. It is regrettable that so notable a contribution to the mech- 

 anism of heredity should have been so long delayed in appearing. 



C. B. D. 



Inheritance of Acquired Mental Characteristics." — A Chicago 

 solicitor of patents has written a book on heredity that is bold and in 

 many respects crude, but which presents so many facts that it war- 

 rants respectful consideration. The subject is the control of the 

 intellectual quality of the offspring by the intellectual activity of the 

 parents. The thesis is that the descendants of intellectually active 

 parents inheret the latter's activity so that, within limits, the more 

 active during a given time the parents have been, or the longer the 

 time of their activity, the more intellectually active the offspring, the 

 greater their chance of achieving eminence. It is nothing new, of 

 course, that the offspring of intellectual or successfully active people 

 are especially apt to have eminent progeny, but it is rather new to 



iRedfield, C. L. Control of Heredity. A Study of the Genesis of Evolution 

 and Degeneracy. Chicago, A. C. Clark, 1903. 8vo. 343 PP-, illustrated. 



