56 



THE AMERICAN NATURALIST [Vol. XLIX 



tage that it does not assume by its form or derivation any hypoth- 

 esis as to the ultimate character, origin or behavior of the deter- 

 mining factor." In adopting the word "Gen*' in the German, 

 Johannsen said: 4 "Das Wort Gen ist vollig frei von jeder Hy- 

 pothese ; es driickt nur die sichergestellte Tatsache aus, dass jeden- 

 falls viele Eigenschaften des Organismus durch in den Gameten 

 vorkommende besondere, trennbare und somit selbstandige 

 'Zustande,' 'Grundlagen,' 'Anlagen' — kurz, was wir eben Gene 

 nennen wollen — bedingt sind. . . . die Gene sehr vieler Eigen- 

 schaften glatt trennbar sind, wahrend andere nicht oder nicht 

 glatt sich trennen. Dies alles erinnert an das Verhalten chemi- 

 scher Korper. Damit ist aber noch gar nicht gesagt, dass die Gene 

 selbst chemische Gebilde oder Zustande seien — dariiber wissen 

 wir vorlaufig noch gar nichts. ' ' How different is all this from 1 1 a 

 minute hypothetical particle"! It is obviously improper, there- 

 fore, to define a gene as a "minute particle. ' ' Neither is it correct 

 to say that it is "supposed to be the bearer of hereditary qual- 

 ities." It is only the something of unascertained nature, which 

 must lie at the foundation of any elementary hereditary quality. 

 The spelling "gene" is not even mentioned in the dictionary as a 

 variant, yet this was the original spelling and is now in practic- 

 ally universal use amonir u'cnet i<-ists. while no one uses "gen." 



Genotype. « « A race of organisms different from another in its hereditary 

 qualities; contrasted with phenotype." 



Genotype. The fundamental hereditary constitution or sum of all the 

 genes of an organism. 



The unfortunate definition of "genotype" given in the dic- 

 tionary was current in America at the time when the dictionary 

 forms were probably closed, so that the editors are not in any way 

 to blame for the totally erroneous definition. The definition given 

 by the dictionary for "genotype" fits fairly well the word 

 "biotype." 



Heredity. "The tendency manifested by an organism to develop in the 



The results of modern experimental work on heredity show that 

 the definition given by the dictionary is entirely too restricted. 

 Heredity must be so defined that it may apply to characters that 

 were never exhibited by any ancestor. 



Heterozygosity. "In Mendelian inheritance, the state or condition due 



* ' 1 Elemente der exakten Erblichkeitslehre, ' ' 1. Aufl., 1909, pp. 124-125. 



