644 THE AMEBIC AN NATURALIST [Vol. XLVI 



The Genotype Conception of Heredity 

 Expressed in Johannsen 's words, the basis of the 

 modern conception of heredity is: "Personal qualities 

 are the reactions of the gametes joining to form a zygote; 

 but the nature of the gametes is not determined by the 

 personal qualities of the parents or ancestors in ques- 

 tion." The quotation expresses well the idea that I 

 have just tried to convey, and from it one sees plainly 

 that it is the correlation that necessarily appears to a 

 greater or less extent between the somatic qualities of 

 two generations when they exist in large numbers that 

 gave the basis for Galton's superficial law. 



This quotation is Johannsen 's slogan for the geno- 

 type conception of heredity. As there stated, it is 

 merely a generalized expression of the essential fea- 

 tures of the Mendelian notation. Johannsen, therefore, 

 was the first to admit the broadness of its scope. In his 

 exposition of his position, however, he adds two sub- 

 sidiary propositions that we will now discuss ; the first 

 is the perennial question of the possibility of the inherit- 

 ance of acquired characters, the second is a question 

 which from its illusiveness is likely to take on a peren- 

 nial habit— that of the relative constancy of unit char- 

 acters. 



In regard to the first question I must be content here 

 with a mere general statement. Like Osborn I would 

 emphasize the possibly delusively static condition of 

 organisms when tested during the infinitesimal time 

 usually devoted to experiment. The inheritance of ac- 

 quirements in some subtle way unknown to us may have 

 been of immense importance in evolution. On the other 

 hand, some sort of an orthogenesis may account for all 

 the facts without the inheritance of acquired characters. 

 It scarcely seems possible that everything is mere chance, 

 though one who has studied plant teratology is as- 

 tounded at the almost infinite number of characters that 

 have appeared that were absolutely dangerous to the 

 individual in its contest for survival. Be that as it may, 

 I simply wish to acknowledge unbelief in any so-called 



