92 



HIGH SCHOOL ZOOLOGY. 





Fig. 68 — Salamandra maculosa, (After Brehm). 



oi'cUnal name Anura. Any of the common species of frog will 

 serve as a type for the recognition of the peculiarities of the 

 order. As to the general form, the absence of the tail, and the 

 great development of the hind-legs along with the webbing of 

 the toes indicate what an entire change in the method of loco- 

 motion is to be observed in them. The short plump body also 

 strongly contrasts with that of the TJrodela. Most of the forms 

 are somewhat brillantly coloured, and have the jiower of 

 altering their colour so as to suit it to the prevailing surrounding 

 hues. This is not the case in the common toad {Biifo lentigin- 

 osus) which remains concealed generally during the day time, 

 but it is very marked in the Wood and Green frogs (Rana teni- 

 j)oraria and clamitans), and in the Ti-ee Toad (Ilyla versicolor ) 

 which, indeed, is very difficult to detect on trees or fences 

 owing to this faculty. The changes in colour are due to the pre- 

 sence of contractile pigment-cells in the skin which are con- 

 trolled by the nervous system. 



17. It can easily be conceived that the change to a new 

 medium must be accompanied by changes in the skin. These 

 chiefly consist in the gi-eater richness of glands which keep the 

 skin moist and allow it to discharge its subsidiary function as a 



