104 CHARLES MIDLO AND HAROLD CUMMINS 



state of pads in the fetus (see discussion) and on the basis 

 of these signs it may be deduced that the fetal pads likewise 

 reach higher development in the palm (with the noteworthy 

 exception of man). 



CONFIGUKATIONAL FIELDS 



It becomes important, having outlined departures from the 

 basic plan observed in the volar pads, to make a similar 

 survey of the several configurational fields. One expression 

 of departure from the plan is the failure of the individual 

 configurational fields to be separately recognizable. The loss 

 of identity of an individual area may be brought about either 

 by the blending of neighboring areas to form a single pattern 

 or by the failure of boundaries between adjoining open fields. 

 It should be clear that an open field having boundaries formed 

 by triradii signifies the individuality of a unit in the morpho- 

 logic plan as effectively as does the occurrence of a well 

 developed pattern occupying the area. On account of frequent 

 individual variations, which may lead to varying completeness 

 of the basic plan among different individuals of the same 

 genus, we can only present for each genus having such varia- 

 bility a characterization of its modal type. In Ateles, for 

 example, the statement that H d and H p are separately recog- 

 nizable applies to the majority of the palms, ignoring the fact 

 that in others H p is represented by a pattern lacking separation 

 from an open field in H d . 



Palm. Separate expressions of H d and H p may be realized 

 through the occurrence of two distinct open fields (occasional 

 in man, represented by the formulation A c Cummins, '35 b), 

 two separate patterns (as in figs. 243-248), or a pattern and an 

 open field separated by a triradial boundary (as in fig. 547). 

 The genera in which these two elements are predominatingly 

 or at least often distinct are : Tarsius (where the fusion of 

 H d and interdigital IV represents another departure from the 

 palmar plan; only in Nycticebus and Nasalis is a similar 

 blending of H d to be found, but here the fusion involves IV" 

 instead of IV proper), Nycticebus, Lemur, all New World 



