No. 551] THE MENDELIAN NOTATION 



645 



proof that the inheritance of acquired characters is im- 

 possible. At the same time one must admit that no un- 

 questionable proof of such inheritance has ever been 

 submitted. Experimental evidence is woefully negative. 

 It seems only reasonable, therefore, considering the 

 available corroborative evidence, to relegate the expres- 

 sion of new characters to variations that have affected 

 the potentialities of the germ cells. We can simply di- 

 vide variations into the classes inherited and non-in- 

 herited without any admission as to their cause. We 

 can call the inherited variations mutations if we will, or 

 we can give them any other name. We must simply re- 

 member that they are both large and small. 



One can hardly agree with Osborn that large varia- 

 tions which are not in an orthogenetic line have had 

 little value in evolution, or that teratological phenom- 

 ena are of little consequence. The production of iden- 

 tical quadruplets in the armadillo can scarcely be a grad- 

 ually perfected character. Zygomorphism in flowers is 

 lost as a unit and although this does not prove its birth 

 as a unit, still that is to be presumed. One could fill 

 pages with such data, but this is hardly the place for it. 

 We will therefore consider the relative constancy of 

 what we know as a unit character. 



The Constancy of Unit Factoks 

 The first thing one does if he wishes to oppose the 

 idea of a unit character is to ask for a definition. A per- 

 fect definition of a unit character is as difficult to formu- 

 late as for a flower, yet one can obtain an idea of a 

 flower by proper application. If one describes a unit 

 character as the somatic expression of a single gametic 

 factor or heredity unit, he at once gets into trouble. As 

 the factor and not the character is the descriptive unit, 

 a unit factor may affect a character but that character 

 may never be expressed except when several units co- 

 operate in ontogeny. I should prefer to disregard the 

 word character therefore in formulating the problem. 

 The real problem is: Are the facts of heredity ade 



