CHIEF MODIFICATIONS OF THE EPIDERMIS 15 



is so much used for digging. Scales are said by a recent writer * 

 to be the earliest condition of which papillary ridges in the 

 Primates are the final development. The species which present 

 scales are Potorous tridactylus, Petrogale -penicillata, Macropus 

 antilopinus, Macropus derbianus, CEpyprymuus rufescens, 

 Myrmecophaga juhata, Talpa europoea, Pteropus medius, 

 Myopotamus coypu. 



(4) Nodules have been only found alone in one species, the 

 Canadian Tree Porcupine, Erethizon dorsatus. The epidermis 

 is in this form modified into very well-defined rounded nodules, 

 which cluster closely over all the palmar and plantar surfaces, 

 the tips of the digits being somewhat corrugated, but without 

 nodules. The modification in this species is very remarkable, 

 and presents an efiicient series of closely-set buffers on the more 

 prominent parts of the hand and foot. It may be noted that 

 the Canadian Tree Porcupine also has a powerful prehensile 

 tail on which there is httle hair on the distal portion, and it 

 is here covered all round with ridges similar to those found on 

 the Primates, but still more resembhng those on the flexor 

 surface of the tails of American opossums. 



(5) Hair. — One species only has been found covered entirely 

 with hair, the Rabbit, Lepus cuniculus. This peculiarity seems 

 to be characteristic of the Leporidse. It furnishes a most efficient 

 method of protection for the footpads, and the rod-hke exten- 

 sions of the epidermis among which the hairs are densely set, 

 serve to conduct sensations to the deeper layer of the skin 

 much in the same way as tactile hairs of other regions. 



(6) Rods. — This arrangement of the epidermis resembles 

 thick, close and short bristles extending from the corium, and 

 is best exhibited in the coarser pads of the large Carnivores. 

 A typical example of this may be seen in the great footpads 

 of the Great Dane. It affords a good protection to the softer 

 parts of the feet in rapid progression over rough ground. The 

 species in which these bundles of rods compose the pads are 

 Thjlacinus cynocephalus, Canis familiaris (Dachshund and 

 Great Dane), Felis leo, Felis domestica, Ursus Americanus. 



* Miss Whipple. 



