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CLASS MYRIOPODA. 



THE CENTIPEDES AND MILLEPEDES. 



Definition of the Class External Structure Internal Structure Reproduction General Habits Fossil Forms Classifica- 

 tion Order CHILOPODA Structure Distribution Habits - - Family SCUTIGERIDA: Family SCOLOPENDRID.K 

 Centipedes Lithobius forficatus Scolopetidra cingulata Geophilus Phosphorescence Order CHILOGNATHA 

 Family JuLiD.E Millepedes Julus salulosus Family POLYOESMID.E Family SIPHONIZA>'TIA Family GLOMEKID.E 

 Order PAUROPODA Pauropm huxleyi Order ONYCHOPHORA PerijMtus. 



THE Myriopoda, commonly known as Centipedes and Millepedes, form one of the most interesting 

 groups of the whole animal kingdom. In the general structure of the body, which in most of them 

 consists of a considerable number of similar segments, they present a close resemblance to the highest 

 forms of the Vermes, the Annelida, and indeed one type that we must refer to the class (Peripatus) 

 would seem to constitute a complete transition between the two classes ; whilst, on the other hand, in 

 the organisation of the uiouth, and the presence of only a single pair of true jointed antennae, we find 



a transition equally complete towards the true 

 Insecta. Some zoologists have dwelt with perhaps 

 undue force upon the analogy between the Myrio- 

 poda and the larvae of insects with a perfect 

 metamorphosis ; but too much importance can 

 hardly be ascribed to the fact that the youngest 

 larvae of some of the Myriopods are furnished only 

 with three pairs of legs, and in other respects 

 much resemble the young of insects with an im- 

 perfect metamorphosis, and above all the Collem- 

 bolous group of the Thysanura. 



The Myriopoda may be defined as Arthropods 

 with a distinct head, and most of the other seg- 

 ments almost pi-ecisely similar to one another, 

 with a single pair of aiitennie, and nearly always 

 with simple eyes, with no distinct thorax, and with- 

 out wings, but with limbs attached to all, or nearly all, the segments of the body. The respiration, 

 as in the insects, is effected by means of tracheae. 



The head, as already stated, is a distinct part, and agrees in general with that of the Insecta, 

 bearing a single pair of antenna?, which are almost invariably simple, jointed organs. The organs cf 

 vision generally consist of simple eyes (ocelli), which, however, are often closely grouped together on 

 the sides of the head. In one family true compound eyes are present. As in the Insecta also, we find 

 three pairs of jaws represented in the mouth, the mandibles being distinct, while the maxilla; and 

 labium are united to form a sort of lower lip, and are thus deprived of all lateral motion. No palpi 

 are recognisable \ipon any of these parts. In one of the orders into which the class is divided the 

 limbs of the first two body-segments take part in the formation of the mouth. The segments of the 

 body are nearly alike throughout ; they are generally horny, and furnished with a pair of jointed 

 limbs. The number of segments varies greatly in the different groups, and even in the genera, the 

 lowest being ten, the highest about one hundred and sixty. In the Centipedes (Chilopoda) we find a 

 slight difference in the character of the first two segments, of which the dorsal part is suppressed or 

 concealed by the head, while the limbs, as already indicated, take part in the formation of the mouth. 

 In the remaining groups the segments are uniform in their development, except that they may become 

 broader towards the middle of the body. The legs, which are usually short, are attached sometimes 

 at the sides of the ventral plates, sometimes close to the middle line of the lower surface of the body. 

 In the latter case each segment bears two pairs of legs, and it becomes a question whether we should 

 not regard the apparent segments as really formed by an amalgamation of two primitive segments. 

 These limbs consist of six or seven joints, of which the last, except in one singular worm-like type, 

 bears a single claw. If we name these joints in accordance with the nomenclature of the parts of the 



PARTS OF MOUTH OF A SCOLOPENDRA. 



A, Mandible ; B, united maxilla; and labiuiu ; c, ttret lair of legs ; 



D, second pair of legs. 



