1888.] NATURAL SCIENCES OF PHILADELPHIA. 101 



separate group of the localities which show special cjisposition to re- 

 tain abundance of hair. Such regions are illustrated by the hairy 

 warts about gular pouches, by the hair of the axilla, of the pudenda 

 and of the perineum. 



The hair of the perineum is commonly distinctly colored in the 

 dog and in some of the lemurs. The highly colored and vascular 

 surfaces of the region of the perineum in the Cynopithecoids are 

 probably created by the same cause. 



The hair of the external auditory canal is associated with ceruni- 

 inous glands. The coarse hair at the base of the nipple may be 

 included in the same category. 



I have found the wrinkles of the skin of the head of the wart-hog 

 (^Phacochoerus aethyojncus) correspond to the black stripes seen in 

 the zebra (Equus zebra). I have no proof, however, that this mark- 

 ing is caused by influence of seba or of moisture. 



The roof of the mouth being black in many mammals induces the 

 observer of pigment patches to include this region under the head- 

 ing of the distribution of color marks on the general integument. 

 It is interesting to note that the efforts of breeders to run out the 

 black from the integument will often result in the loss of pigment 

 from the roof the mouth. That the oral surface is capable of 

 yielding special outgrowths which are comparable to those of the 

 skin is shown in Balaena and many rodents. 



4. Effects of Age. — That the color marks of young animals 

 frequently differ from the adult forms is a matter of common obser- 

 vation. The relations existing between the young of one species and 

 the adult form of others have been often observed but need further 

 elucidation. The white collar at the base of the neck in some dogs 

 is seen in the young form only of the bear. The change in the 

 Himalayan rabbit from white, to white with dark markings has 

 been already noted. 



The corresponding changes which take place in the animal in old 

 age has received much less attention than it deserves. The few ob- 

 servations I have made confirm the statements made elsewhere 

 respecting the orientation of pigment patches. Horses often 

 become gray in the circumpalpebral regions before they change 

 elsewhere. An Italian gray-hound, which I have observed for a 

 number of years, displays as it advances in senility a dorsal white 

 stripe, a white star on the breast, a circumpalpebral gray patch and 



