92 H. H. COLLINS 



ventral surfaces are practically nil. Then, too, the dorsal surface 

 of the tail is rarely wholly covered by the median stripe. Here, 

 under identical conditions of illumination, heavily pigmented 

 and pigmentless hairs develop side by side. 



Furthermore, I have observed no differences in the color of 

 hairs of the shaded margins and of the exposed central portions 

 of depilated areas. The capacity for the production of hairs of 

 the agouti type appears to be quite definitely confined to the 

 dorsum, the position of the lateral line apparent^ being unaffected 

 by the operation. Recognizing the fact that in a large number 

 of cases the markings of animals obviously cannot be attributed 

 to differences in intensity of illumination, Schultz has recourse to 

 a second theory, namely, that such color markings are due to the 

 inequalities in the peripheral blood supply. The black markings 

 of the Himalayan rabbit are found on the extremities where the 

 blood supply is somewhat reduced. The dorsal median stripe 

 found in many mammals, in Peromyscus for example (figs. 7, 9, 

 15), is said to be due to the pressure on the skin of the underlying 

 vertebrae, which impedes the circulation. The rings on a cat's 

 tail overlie vertebral processes, and so on through the category. 

 It must be pointed out in this connection that Schultz appears 

 to be somewhat inconsistent in his application of this theory. 

 In one paragraph we read : 



Maine Ergebnisse, dass wachsendes Haar besonders fiir Farbstoff- 

 bildung geeignet ist, und zwar um so mehr, je lebhafter die Wachstums- 

 vorgange, sind eine Art Nachahmung der von Darwin bemerkten Natur- 

 erscheinung, dass weisse Taubenrassen unbefiedert, dunkle ])efiedert 

 dem Ei entschliipfen. Die Kaninchenalbinos, die ich hielt, schienen 

 niir bei der Geburt auch so gut wie kahl, die farbig geborenen Rassen 

 aber starker behaart. 



In vielen Naturmustern finden wir die starksten Farbstoffanhaufun- 

 gen gerade an Stellen, die durch starkstes Haarwachstum gekennzeich- 

 net sind, und an solchen Vorspriingen und Ausbeutelungen der Haut, 

 die zeitweilig starker wachsen mlissen als ihre Umgebung, z. B, Mahne, 

 Schweif und Beine der Grauschimmel (p. 161). 



However, in regard to the black markings of the Himalayan 

 rabbit, he writes : 



