86 THE SENSE OF TOUCH IN ANIMALS 



MONOTREMES. Ornitliorhynchus (Fig. 53).— This section 

 is taken from a piece of the skin of the hind foot, which had 

 been kept in alcohol for a considerable time and perhaps on this 

 account may show too little differentiation of the skin-structures, 

 but it would seem to have a simple epidermis and papillae of the 

 corium poorly developed. 



Echidna (Fig. 54). — Section from forefoot. Papillse of the 

 corium, numerous and well-pointed, irregular grooves on the 

 epidermis resembhng papillary ridges. 



MARSUPIALS. Didelfhijs Azarce. — Fig. 55 gives a longi- 

 tudinal section of the terminal phalanx of a digit of the fore- 

 foot, and at the right-hand side or tip of the phalan;x: are seen 

 some rudimentary papillary ridges on the epidermis and corre- 

 sponding papillse of the corium. 



Fig. 56 is from the hind foot on the plantar surface through 

 a whorl of papillary ridges situated on an interdigital pad. Well- 

 developed ridges, bifurcated or double papillse of the corium and 

 large Drlisenleisten are seen. This is a development of the 

 skin-structures in a low Marsupial much beyond that of many 

 higher forms between this group and the Primates. 



Thylacinus cynocefhalus (Fig. 57). — Section from large palmar 

 pad of forefoot. Presents a rough irregular surface of the epi- 

 dermis, not unhke those of Carnivores, and papillse of the corium 

 pointed, and formed very much as those of many Carnivores. 



Trichosurus vulpecula (Fig. 58). — Longitudinal section through 

 transverse papillary ridges on terminal phalanx of a digit of the 

 hind foot. Ridges a little irregular, papillse of the corium and 

 Drlisenleisten well-formed. 



Fig. 59 from plantar surface of hind foot ; section through 

 rows of scales, not formed here into papillary ridges. Each 

 separate scale except two in centre of section, shows papillse 

 of the corium bifurcated by a well-formed Driisenleiste. 



Fig. 60, forefoot, tip of digit, longitudinal section through 

 large well-formed papillary ridges, bifurcated papillse of the 

 corium and large Drlisenleisten. 



Fig. 61, a longitudinal section from the under-surface of the 

 tail, through transverse rows of scales resembling coarse j)apillary 



