PROCEEDINGS OF THE OHIO ACADEMY OF SCIENCE. 367 



general type of development and the sperm and egg nuclei sup- 

 ply only the details. We are vertebrates because our mothers 

 were vertebrates and produced eggs of the vertebrate pattern ; 

 but the color of our skin and hair and eyes, our sex, stature, 

 and mental peculiarities were determined by the sperm as well 

 as by the egg from which we came. There is evidence that the 

 chromosomes of the egg and sperm are the seat of the differential 

 factors or determiners for Mendelian characters, while the gen- 

 eral polarity, symmetry, and pattern of the embryo are deter- 

 mined by the cytoplasm of the egg". 



And, in broader terms, granting that certain characters fol- 

 low the Mendelian type of alternate inheritance, are all charac- 

 ters Mendelian in heredity? Seemingly we have some startling 

 exceptions. For example, the crossing of Negro and Caucasian 

 gives an f^ generation of Mulattoes, intermediate in their skin 

 color between the parent stocks. This may be explained in 

 Mendelian terms through the absence of dominance. Numerous 

 parallel cases are known in which the inheritance is otherwise 

 strictly Mendelian. More serious is the recognized fact that the 

 fa generation of Mulatto paired with Mulatto does not segre- 

 gate into the Mendelian proportion of i Negro : 2 Mulattoes 

 : I Caucasian. Here Mendelian segregation has apparently 

 given way to complete blending; and this is not a solitary case, 

 but can be duplicated alike from plant and animal breeding. 

 Orthodox Mendelians meet the difficulty by the assumption of 

 multiple factors, — several independent factors each of which 

 may produce a given character, although in varying degree of 

 intensity according to the number of the factors present in the 

 individual case. With two such factors for dark color there 

 would be but one pure black and one pure white in sixteen of 

 the i^ generation, the other fourteen being of intermediate de- 

 grees of darkness ; with three such characters there would be 

 one pure black and one pure white in sixty-four ; while, in the 

 theoretical extreme, an infinite number of such characters would 

 reduce the pure whites and pure blacks of the f, generation to 

 more than infinite rarity. This reductio ad absurdum may be 

 an unfair treatment of the Mendelian explanation ; but it must 



