DERMATOGLYPHICS IN PRIMATES 173 



tionary sequence to bring about permanently elevated pads, 

 but early enough to influence a more prolonged fetal reten- 

 tion. Following the same line of conjecture, the Old World 

 monkeys might have stemmed from an arboreal stock at a 

 period so early that the pads still possessed all the potentiali- 

 ties necessary to regain full primitiveness even after they had 

 been modified under the circumstances of arboreal life. In 

 our consideration of primate affinities resort has been made 

 only to descriptive standards of primitiveness, inasmuch as 

 it is impossible to evaluate these speculations and to determine 

 whether a descriptively primitive condition is primary or 

 secondary. 



The processes of ridge differentiation in the fetus are of 

 such nature that specific configurations are mere by-products, 

 their qualities fluctuating in accord with the ontogenetic 

 mechanisms which determine them rather than being regulated 

 by factors which are associated with the configurations them- 

 selves. What constancy there is in the configurations is the 

 correlate of the degree of constancy in the reliefs of the 

 surface. We have dealt principally with configurations which 

 are identified with volar pads. It is the systematic topography 

 of these pads which accounts for the existence of the dermato- 

 glyphic plan, and all departures from that plan may be 

 readily explained on the basis of varying behavior of the 

 pads at the time of ridge formation or prior to it. If the 

 variations of the palmar and plantar dermatoglyphics were 

 not restricted by the limits of variation of the pads, their 

 expressions of specific configurations on the palm and sole 

 would show no systematic order. With no local irregularities 

 of relief at the time of ridge differentiation, the configuration 

 would be as monotonous as that shown in a sole of gibbon 

 (fig. 499), neither patterns nor vestiges being present to dis- 

 turb the expanse of this continuous open field. Were there 

 unsystematic irregularities of contour the surface might on 

 the other hand be marked by erratic local patterns and ridge 

 disturbances resembling those seen in the tail of Lagothrix 

 (figs. 594, 595). 



