SKIN. 



553 



different species. The anus is always at the posterior end of 

 the body, and the generative opening is on the ventral surface 

 just in front of the anus ; it may be between the legs of the last 

 or penultimate pair (Fig. 332), or it may be behind them. There 

 is in most species a thin median white line extending the whole 

 length of the dorsal surface of the body, on each side of which 



FIG. 332. Ventral view of hind end of 



P. novae-zealandiae (after Sedgwick). 

 g generative opening ; a anus. 



FIG. 333. Ventral view of the head of P. 

 capensis (after Sedgwick) : ant antennae ; 

 or.p oral papillae ; F.I first leg ; T 

 tongue. 



the skin pigment is darker than elsewhere. The skin has a 

 velvety texture and the colouring, which is always remarkable, 

 varies considerably in the different species, and even in different 

 individuals of the same species. The ventral surface is nearly 

 always flesh-coloured, while the dorsal surface has a darker 

 colour. In the South African species the colour of the dorsal 

 surface varies from a dark green graduating to a bluish gray, 

 to a brown varying to a red orange. The colour of the Aus- 

 tralasian species varies in like manner, while that of the Neo- 

 tropical, Malayan and New Britain species is less variable. The 

 brown ground pigments are dissolved by spirit, but the other 

 pigments are not appreciably affected. 



The skin is thrown into a number of transverse ridges, along 

 which wart-like papillae are placed. The papillae, which are 

 found everywhere, are specially developed on the dorsal surface, 

 less so on the ventral. Each papilla carries at its extremity a 

 weU-marked spine. The cuticle which covers the body is 



