140 CHARLES MIDLO AND HAROLD CUMMINS 



proximal groups are progressively lowered in relative in- 

 tensity represents the least modified regional relationship. 

 While this sequence is itself somewhat modified, with reference 

 to a theoretically more primitive condition in which all groups 

 would be equal, it appears to be the strongest claimant for 

 recognition as the simplest available basic order. Significant 

 disorganization of that order may be taken to indicate pro- 

 found regional specialization. Quite apart from any question 

 which might arise as to our setting up the regular disto- 

 proximal order as a standard of reference, it will be obvious 

 that reversals such as are to be seen in Hylobates are ac- 

 ceptable evidences of regional specializations which differ 

 from that standard. In the instance of Hylobates, it 

 might be proposed that the extreme reduction of pattern 

 intensity in the distal series is linked in some way with 

 brachiation, notwithstanding that Ateles, though also a 

 brachiator, adheres to the regular gradient of intensity in these 

 three groups. The conditions in Pongo, another brachiator, 

 resemble those described in Hylobates, and it may be added 

 that the distinctiveness of the sole in Hylobates is approached 

 by the sole of Pan. To single out the generic departures from 

 the simple gradient order is thus not very fruitful if an 

 attempt be made to correlate them with specific locomotor 

 habits, however convincing it may be that these departures do 

 indicate specializations. 



RELATIONSHIPS TO THE ANATOMICAL AXIS 



Of special interest in a consideration of regional variations 

 of pattern intensity is the relationship to the anatomical axis 

 of hand and foot. Interdigitals II, III and IV are best adapted 

 to this comparison. In figure 599D it will be noted that in 

 non-human primates the average values of these areas are 

 such that in both hand and foot interdigital III presents a 

 lower value than either II or IV. Inspection of the values for 

 individual genera (tables 4 and 5) will show that with few 

 exceptions they conform to the average. The exceptions of 

 particular interest occur in the soles of Lemur, Saimiri, 



