No. 573] 



PATTERN DEVELOPM EN T 



561 



18 and 19 it appears at the end of the tail. In the former 

 figure the sacral patches are much reduced, though pres- 

 ent, and tog-ether spread nearly half the length of the tail. 

 The terminal half, or less, of the tail, however, is dark- 

 pigmented, and a break occurs between the two sorts of 

 markings, due to the failure of the centripetal patch to 

 spread so as to unite with the centrifugal area. In Pig. 

 1!) the sacral patches have wholly failed to develop but 

 the centrifugal patch still covers the distal half of the tail. 

 Possibly the dark heel marks in Fig. 16 are patches devel- 

 oped in the same way. In the house cat, a dark or 

 "smutty" nose is often present in contrast to an other- 

 wise white face, or with the ear patches only slightly 

 reduced. In the breed of rabbits known as "Himalayan. " 

 the centrifugal pigmentation remains, though the centri- 

 petal markings have disappeared, so that it is pure white 

 except for the black nose, ear tips and toes. No doubt, 

 however, it wpuld be possible for the two types of pig- 

 mentation to appear in a single individual. This is sug- 

 gestive of the winter phase of the Arctic hares, in which 



color is retained throughout the winter, instead of being 

 replaced by white — again a persistence of black pigment. 

 In dappled gray horses a black patch sometimes appears 

 on the bridge of the muzzle, usually the first place to show 

 white in the restriction of centipetal pigmentation. The 

 feet may also be black. Among certain antelopes a black 

 muzzle mark is similarly present, and in Hunter's ante- 

 lope (Da niali sens hit uteri) a white border partly sur- 

 rounds such a mark. This, I believe, is due to a slight 

 restriction of the ear patches, sufficient to prevent them 

 from reaching the muzzle, and of about the same nature 



through the absence of a centrifugal nose patch, the entire 



the 



in occasional welau- 

 'ing hare, the black 



