CHAPTER VIII. 



FROGS, TOADS, AND NEWTS. 



THERE is no vertebrate animal whose anatomy has' 

 been more thoroughly investigated and described than 

 the Common Frog, Rana temporaries. The specific name 

 refers to the large black patch on the temporal region 

 of the head. The general colour of the animal, and 

 especially of its dorsal surface, is liable to great variation, 

 not only in different individuals, but in the same individual 

 on different occasions. The most usual coloration is 

 perhaps a mottled green and brown, but all conditions 

 between yellowish-red and dark brown-black are of frequent 

 occurrence. The markings upon the hind legs are chiefly 

 transverse. The ventral surface is yellow, pale or bright, 

 and is sometimes spotted. The colours are due to stellate 

 pigment-cells, that occur sparsely in the epidermis but 

 abundantly in the loose layer of subcutaneous connective 

 tissue. Nerve fibres pass into direct connexion with these 

 cells, and by appropriate impulses regulate their shape, 

 causing them to contract to mere pin-points or to spread 

 out over a relatively large area according as it is necessary 



