DEEMATOGLYPHICS IN PRIMATES 171 



bases and are somewhat more yielding, closely resembling 

 the conditions of pads in monkeys with pronounced walking 

 habit. 



In primates there is extreme diversity with regard to modifi- 

 cations of pads. Never are these eminences, except in some 

 prosimians, so prominent and so discrete as in typical quad- 

 rupeds. The outstanding modifications are lowering or com- 

 plete suppression, and fusions of adjoining pads. Also in 

 primates the pads are more yielding than in typical quad- 

 rupedal mammals. The lowering and yielding consistency 

 facilitate the prehensile use of the member. The dermato- 

 glyphic variations in primates are reflections of modifications 

 of the pads, though it is in the fetal period that the impress of 

 the relationship between pads and dermatogiyphics is effected. 

 Individual configurational variation is reduced to a minimum 

 in primates which retain conspicuous pads in the adult, and 

 in those forms which may be assumed to have passed through 

 a much accelerated subsidence of pads in the fetal period 

 (Hylobates). These reductions of individual variability are 

 associated with the utmost stability of volar pads in the 

 fetus, in the one instance expressed as the maximum retention 

 of fetal pads and in the other the maximum and earliest sup- 

 pression. Since there must exist some degree of chronological 

 variation in subsidence of pads, such variation would be ex- 

 pected to reach its extreme in those forms which present only 

 slightly marked pads in the adult, as in Gorilla, Pan and Homo. 

 The known history of regression of pads in the fetal period 

 of man suggests that the pads are involved in a still active 

 phase of phylogenetic involution. If this be true, the high 

 individual variability in the regressive behavior of pads in 

 man, and assumedly in Pongidae as well, is comparable to the 

 variability of other anatomical features that are develop- 

 mentally labile because of their involvement in an uncompleted 

 evolutionary process. That is to say, such pads, being neither 

 completely retained in further development, nor totally sup- 

 pressed prior to ridge differentiation, should be quite incon- 

 stant at the time of ridge differentiation. That this is the 



