1888.] NATURAL SCIENCES OF PHILADELPPIIA, 105 



clianoje must cause variations in the rates of growth in accession or 

 repression of force which will call into activity one or more of the 

 proclivities above named. The extreme variety of this individual 

 experience doubtless explains, the great difference seen in the ways 

 that animals are colored. 



The fact that coloration is limited, or that it is apt to be limited, 

 to the points of convergence of Eschricht and Voigt would appear 

 to be a tentative conclusion. The careful study of the peculiarities 

 of the animals which are born naked would probably greatly 

 strengthen it. 



I will conclude by making the suggestion that the distribution of 

 color-marks along the directions already indicated is a larger phase 

 of the subject of evolution than is outlined by "mimeticism" and by 

 "natural selection." I assume that Ailuropus doeS not, for the reason 

 that it cannot, change the black feet, the black auricle and the black 

 circum-ocular region for one in harmony with the ground color, not- 

 withstanding the disadvantage to which the contrast between the 

 black and white subjects him. I also assume that the breeders of the 

 dog cannot run out the black from the skin over the sacrum and 

 the root of the tail with the same ease he can determine many other 

 colors. According to natural selection and domestication the vari- 

 ous regions above named explain the frequent occurrence of colors 

 which are of great use to the individual but they often meet with 

 abrupt limitation owing to the influence of deep-lying restraining 

 causes. 



occurrence of acne pustules or syphilitic papules in positions in which the marginal 

 warts occasionally appear, — the retention of the hair near the bregma and at the 

 occiput m instances of loss of hair other than from age, can be noted in studying 

 the distribution of eruptions upon the skin and of naevi as well as of color marks. 

 But the field of observation is difficult when the conditions are often so fleeting. 

 The impressions of a single observer are not sufficient to secure definite conclusions: 

 For information, including literature of this phase of the subject, the reader may 

 refer to the experimental researches of A. Irsai and V. Babesin i upon the influence 

 of the nervous system upon the pathological conditions of the skin, and to T. 

 S. Dowse on the nervous affections of the skin and its appendages.2 



1 Vierteljahresschr. f. Dermatol, u. Syphil. 1882, IX, 433. 



2 Med. Press and Circular 1879, I, 499. 



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