262 THE AMERICAN NATURALIST [VOL. XLIII 



reading the classification into nature and to the over- 

 looking of transitional stages, and we shall therefore en- 

 quire if the distinction which is made between elementary 

 species and varieties is a valid one. 

 \ In the first place, there does not seem to be any very 

 good reason why on the pangen theory elementary species 

 should differ in numerous characters from the parent 

 form. A pangen is the basis of a single unit character. 

 Elementary species are produced through the origination 

 of a new kind of pangen. / If the becoming latent or 

 dominant of a pangen affects only one unit character of 

 an organism, it is not evident, when a new kind of pangen 

 is produced, why the whole organization of the plant 

 should be so profoundly influenced. Why should not the 

 awakening of a dormant pangen produce as great a 

 change as the production of a new pangen of a somewhat 

 different quality. Says De Vries : 



There can be little doubt but that all the attributes of every new 

 species are derived from one principal change. But why this should 

 affect the foliage in one manner, the flowers in another and the fruits 

 in a third direction, remains obscure. To gain ever so little insight 

 into the nature of these changes, we may best compare the differences 

 of our evening primroses with those between the two hundred ele- 

 mentary species of Draba and other similar instances. In doing so 

 we find the same main feature: the minute differences in nearly all 

 points. 



De Vries nowhere gives us a much clearer explanation 

 as to why elementary species and varieties should differ 

 in this way and we must probably be content with re- 

 ferring the matter to different degrees of "correlation." 



It is evident that there are allied groups separated by 

 small differences throughout the entire organization, and 

 there are other groups which differ apparently in single 

 characters only, such as the presence or absence of hair, 

 spines or certain colors. Hornless cattle and six-toed 

 cats do not seem to present any general or constitutional 

 differences from the other members of their species, but 

 this is a subject upon which we should exercise great 

 caution, as very slight differences in the rest of the organ- 



