( 311 ) 



that followed by the limitlines of the segments of the skin. The 

 number of the stripes, however, is greater than that of the segments 

 can possibly be. But for this ditïiculty too a solution can be found. 

 On considering the curve of sensibility of a normal trunk-skin, as it 

 has been constructed by Winklkr and myself on tlie basis of our 

 experiments, we find thai at the dorsal median line, where the 

 central areas overlap one another on an average for one third and the 

 dermatomata for one half, a top of the curve i. e. a zone of 

 summation corresponds with every average limit-line between two 

 dermatomata. If now the overlapses amount to more than one half, 

 as they do on the extremities, the curve of sensibility will be much 

 more complicated and the zones of summation therefore more nume- 

 rous. Accordingly the dark stripes on the extremities correspond 

 likewise with the average lines of demarcation of the dermatomata. 

 In the zebra the excedent of pigment apparently is distributed in 

 accordance with the scheme of the intersegmental zones of summation, 

 and the design resulting from this distribution may therefore be 

 defined as consisting of intersegmental excedent-contrasts. Although 

 this instance may not be entirely isolated, still it is a rather rare 

 one. In many other cases we find that the excedent of pigment is 

 not distributed in accordance with the uniform scheme of inter- 

 segmental demarcation, but arbitrarily accumulated in certain 

 points or portions of the segments themselves. A large number of 

 white domestic animals for instance present black spots, showing a 

 marked similitude in their shape, distribution and extension with the 

 figures, denominated by Winkler caricatures of the dermatomata. 

 The way in which the pigment is distributed, oifers even an indication 

 of that peculiar significance which the point of entrance of the skin- 

 nerve apparently possesses for the innervation (maximum and 

 ultimum moriens of the central areas, of the dermatomata and of the 

 sensible skin-areas in general^)). Thus the series of black dots in many 

 species of sharks, amphibians, serpents and saurias, apparently corre- 

 spond nearly with the serial ranging of the points of entrance of the 

 dorsal and lateral nerve branches. 



We will now turn to the defect contrasts. In deepcoloured speci- 

 mina of our domestic animals white-tipped ears or tail, a white belly, 

 or a white mark in the frontal median line of the head, or else 

 white toes, are frequently to be met with. It needs not being demon- 



^) On function and etc. These Proc. Vol. VI, p. 3i7. G. van Runberk: On the 

 fact of sensible skin areas dying away in a centripetal direction. These Proc> 

 Vol. VI, p. 346. 



