CLASS II. MYRIAPODA: ORDER 2. CIIILOrOLA, 



599 



double thread; the circulation is effected by a long, cylindrical, dorsal vessel. The species 

 are all unisexual. In some kinds the young, on first escaping from the egg, possess nearly ail 

 the characters of their parents, although the number of segments and limbs is always less, and 

 increases at each change of skin ; but some, as the /«//, undergo a sort of metamorpliosis, coiniuo- 

 from the egg either quite destitute of feet, or furnished with only three pairs of these organs, 

 and it is not until after several moultings tliat they attain the same number of legs as their 

 parents. This metamorphosis, such as it is, indicates the close alliance of these creatures with 

 the insects ; and many authors either include them in the class Insecta or retain them in a sepa- 

 rate class. The Myriapoda form two orders, the Chiloijnatha and the Chilojioda ; of the former 

 there are over seventy sj^ecies ; of the latter about one hundred. 



ORDER 1. CHILOGNATHA. 



In these the body is generally of a convex form, composed of numerous homy arches, below 

 which an immense multitude of little feet may be seen, whence the name of MillcpedeH^ or Thou- 

 saiid-lc(/s, by which these animals are commonly known, is derived. Each segment of the body 

 bears two pairs of limbs, with the exception of the hindmost segment, which is destitute of such 

 organs. The antennae are short, and composed oidy of seven joints, and the jaws are reduced to 

 a rudimentary condition. The species are found to feed principally upon vegetable matters, 

 generally when in a state of decay. Their movements, notwithstanding their immense number 

 of legs, are always very slow, and they generally endeavor to escape danger by rolling themselves 

 up into a ball. There are several families belonging to this group, but the best-known species is 

 the Gally-Worm, lulus terrcstris, often found, like the rest of the tribe, in damp moss, and 

 sometimes crawling over the trunks of trees. The /. maximus of Brazil is often seven inches 

 long. The Glomeridce, belonging to this order, resemble wood-lice. 



THE ELECTKIC SCOLOPENDRA. 



ORDER 2. CHILOPODA. 



These animals are usually of a flattened form, and live in the earth or under stones. They 

 run with considerable swiftness in pursuit of their prey, and can even progress backward by the 

 assistance of their tail-like hind-legs, which at other times are dragged helplessly behind them. 

 Their food consists of insects, which they seize with the powerful jaw-like organs attached to 

 the lower lip. There are various kinds, but the most remarkable ftimily is that of the Scolojjen- 

 dridce, commonly called Centipedes : they are nocturnal in their habits, prey on insects, and are 

 active and voracious creatures. Some of these, in tropical climates — as for instance the Malfai- 

 sante, a West Indian Scolopendra — grow to the length of six inches, and certain wi'iters say 

 to twice that size. Their bite is very painful, and sometimes fatal. The smaller and hai'inless 

 species, common among us, are found at night concealed under timber or in holes in walls. 



The Electric Scolopendra, S. chctrko, is a European species, luminous in the dark. 



The Geophilidce have almost thread-like bodies, some species of which are phosphorescent. 



The species of Scutigera have the body divided into fifteen segments, each bearing eight 

 pairs of long multi-articulated legs; they are very active, and oiten lose some of their legs when 

 touched. Those of the genus Lithobius have the body above and below divided into the same 

 number of segments, each of which bears a pair of legs. 



