32 A BOOK OF INSECTS 



geners, the second the millipedes and pill-millipedes. 

 Both these classes stand apart from, and are simpler than, 

 the others. The members of each have only one body- 

 ring added to the head, and only one pair of " foot-jaws." 

 The appearance of millipedes and their allies (termed 

 Diplopoda because they have two pairs of legs on each 

 segment of the body) must be familiar to the reader, but 

 Peripatus and its kindred, which constitute the class 

 Peripatoidea, call for a brief description. Professor 

 Adam Sedgwick tells us that these curious animals live 

 beneath the bark of rotten tree stumps, in the crevices of 

 rocks, and beneath stones in South Africa, New Zealand, 

 Australia, South America and the West Indies. They 

 differ from all other Gnathopods in possessing certain 

 worm-like peculiarities, notably in the softness and 

 pliability of their skin. Nevertheless, their appearance is 

 distinctly pleasing. "Peripatus" (says Professor Sedgwick), 

 " though a lowly animal, and of remarkable sluggishness, 

 with but slight development of the higher organs of 

 sense, with eyes the only function of which is to enable 

 it to avoid the light — though related to those animals 

 most repulsive to the aesthetic sense of man, animals 

 which crawl upon their bellies and spit at, or poison, 

 their prey — is yet, strange to say, an animal of striking 

 beauty. The exquisite sensitiveness and constantly 

 changing form of the antenna?, the well-rounded plump 

 body, the eyes set like small diamonds on the side 

 of the head, the delicate feet, and, above all, the rich 

 colouring and velvety texture of the skin, all combine to 

 give these animals an aspect of quite exceptional beauty." 

 Two other classes (or shoots from the main stem of 

 foot-jawed animals) are called respectively the Arachnida 

 and the Crustacea. The former class includes, among 

 less familiar creatures, the king crabs, spiders, scorpions, 



