No. 509] THE CATEGORIES OF VARIATION 283 



About the only criterion l>y which they may be recognized 

 is their stability, and even that gives some evidence of 

 being a matter of degree. No limit has been discovered 

 to the minuteness of the stable modifications that may 

 occur, and it may happen that further study will reveal 

 the comparatively frequent appearance of very slight 

 variations of this kind. In fact, considerable progress 

 has even now been made in this direction by the stndv of 

 grains ; and the number of more or less stable modifica- 

 tions that are likely to be discovered threatens to over- 

 whelm systematists with the labor of naming and describ- 

 ing them. In many organisms not propagated by self- 

 fertilization the detection of these small steps is no easy 

 task and the attempt to describe them all would undoubt- 

 edly prove a futile effort. Among human beings, for 

 instance, what are we to designate as elementary species .' 

 We meet with all grades of differences from well-marked 

 family traits to those which separate the Caucasian from 

 the negro. Are we to regard the Hapsburg lip which 

 was transmitted with fidelity for many generations as 

 the mark of an elementary species? It was apparently 

 a new character and therefore presumably dependent 

 upon a new pangen or determinant. The Celts, Teutons, 

 Slavs, etc., differ by more or less constant characters 

 which are constitutional and not confined to single parts, 

 and the same may be said of the various subdivisions of 

 these groups. The Aryan stock to which these groups 

 belong is separated by still greater differences from the 

 other subdivisions of the Caucasian race, and the latter 

 in turn differs still more widely from the negroes and 

 Mongolians. One has considerable difficulty in disposing 

 of these groups either as varieties or elementary species. 

 They can not from De Vries standpoint be considered 

 the results of fluctuating variability on account of their 

 constancy even under very varied external conditions. 

 If the small divisions have arisen by slow changes, as 

 everything indicates, there is no logical halting place 

 short of admitting that the greater ones may have done 



