84 



EVOLUTION AND GENETICS 



relatively rare, but are commonly found on the feet and tails of 

 such animals as rodents, and in the armadillo and a few other 



a 



I • •«.« 





e 



• • • 



'•'• • 



• • • 



•'•'• 



• '• 



' • • .• • 



i.y '■:■) 



m mm 



^ - -r. • *t« 



Fig. 58. — Hair pattern in mammals, diagrammatic, a, tail of Myopotamus, 

 a South American rodent, with scales and hairs; b, back of Midas, a Bra- 

 zilian monkey; c, back of pig, Sus vittatus; d, back of Coelogenys paca, a 

 South American rodent; e, back of Dasyurus viverrinus, an Australian 

 marsupial; f, back of Loncheres cristata, a South American rodent. (From 

 Wilder's History of the Human Body, after de Meijere; with the permission 

 of Mrs. H. H. Wilder and Henry Holt and Company.) 



mammals the dorsal surface is covered with them. These scales 

 are also similar in form and derivation to those of the birds and 

 reptiles, but are usually less horny. Hair is very different from 



