1887.] NATURAL SCIENCES OF PHILADELPHIA. 59 



In a number of mammalian orders, there is a marked tendency 

 toward a dorsal, longitudinal striation, or linear alternation of bands 

 or dots of color, and in a numl)er of cases, this striation is well 

 marked only in the young. This seems to be more than a mere co- 

 incidence and probably indicates that in the primitive or ancestral 

 Mammalia, such a pattern was widely prevalent, if not universal. 

 On the sides, on the other hand, there is a tendency toward alterna- 

 ting vertical colors with transverse bars on the limbs. This is a 

 well-marked feature in the tiger, zebra and gnu. Later on it ap- 

 pears that these bars have broken up into dots, giving rise to the 

 dappled or the spotted appearance of such forms as the leopard, 

 giraffe and horse. These features have a very important phylogen- 

 etic significance, and point to an ancestral form, in which the color 

 areas were disposed in bands. Looking about, amongst the lower 

 groups, it is in Reptilia alone that we frequently find striping both 

 longitudinal and transverse, and in thaf it is now admitted by some 

 eminent authorities that the Mammalia are descended from the 

 Reptilia (Therojnoiyha), some explanation is afforded of the preva- 

 lent type of color marking in the young of many feral Mammalian 

 forms which are not striped when mature. 



The dorsal longitudinal rows of hair germs in the skin of the 

 foetal cat also aflTord confirmatory evidence. Their coincidence with 

 the bands of color and precocious development, indicates that they 

 are remnants of a more primitive hairy coat. Their linear arrange- 

 ment makes it possible to compare them with the linear and longitu- 

 dinal arrangement of the feathers in birds and of scales in reptiles. 

 In that hairs of mammals, feathers of birds and the corneous scutes 

 of reptiles, are closely related structures and developed from homol- 

 ogous layers of the epidermis in these different classes, it is highly 

 interesting to discover that the set of hair germs, which are the first 

 to develop on the back of the foetal cat, also show the primordial, lin- 

 ear arrang-ement of scales and feathers as observed on the backs of 

 reptiles and birds. 



