( 3J3 ) 



a new support to the probability of the hypothesis tliat a segmental 

 basis lies at the root of many pathological states, as naevus 

 'pigmentosus etc. 



CONCLUSIONS. 



1. The distribution of the pigmentation on the skin of vertebrated 

 animals is in a large series of cases the expression of pecnliar rela- 

 tions in the segmental innervation of the skin. 



2. In the "skin-design" taken in its widest acceptation, three 

 elements ought to be distinguished -. the prime-colour, the excedent- 

 contrast and the defect-contrast. 



3. In animals, whose skin is nearly wholly of one colour, (he 

 excedent-con trast may be zonal (dorsal) or isolated. 



An isolated contrast frequently corresponds : 

 for the head 



a. with a definite central nerve-area: (the excedent-contrast in 

 the N. trigeminus), or else with definite portions of these areas (Point 

 of entrance of the nerve in the hypodermis; the excedent-contrast 

 ex introitu; the supraorbital mark), 

 for the remainder of the body : 



h. with definite isolated skin-segments, more pigmented than the 

 other segments, or with definite sub-divisions of these segments 

 (caricatures of the dermatoma; segmental excedent \'ariability ; seg- 

 mental excedent contrast). 



c. \vith zones of intersegmental summation (intersegmental excedent 

 contrast; the cross on the back of the ass). 



4. The defect contrast in animals that are nearly wholly of one 

 colour maj^ appear as a lack of this colour either zonal (ventral) or 

 isolated. The isolated defect contrast frequently corresponds with : 



a. definite nerve-areas, being situated very eccentrical, either in 

 absolute or in relative sense. (Tip of the tail, tips of the ears, ventral 

 median line, frontal median line of the head, toes; they are all 

 specimina of eccentrical defect-contrasts). 



b. with definite non-pigmented skin-segments (phenomena of seg- 

 mental-omission, segmental defect variability, segmental defect-contrasts). 



5. Eimer's type of the transversally striped animals ought to be 

 divided into two sub-divisions : 



a. animals with broad, dark transversal stripes, which are less 

 numerous than the segments of the body (fishes, sauria's, serpents). 

 These broad transversal stripes correspond probably with groups of 

 strongly pigmented segments, alternating with other groups that are 



