5 8 MYRIAPODA 



CHAP. 



5. The next pair of appendages are the first pair of the legs 

 of the body, which are also metamorphosed to serve 

 a function different from the ambulatory function of 

 the other limbs. These are the poison daws, and the 

 possession of these forms another distinction between 

 the Order we are now discussing and that of the Chilo- 

 gnatha. At the same time the third Order, that of the 

 Schizotarsia, has poison claws, so that this feature does 

 not separate the Chilopoda from all the other Orders. 

 These poison claws are large curved claws connected 

 with poison glands, the secretion of which flows through 

 a canal which opens near the point. 



The legs are longer than those of the Chilognatha, but not so 

 long as those in the next Order to be described (the Schizotarsia). 

 Their number is very various, from 15 pairs in Lithobius to 173 

 in the Geophilidae. Latzel notes a curious point in the number 

 of the legs in this Order, namely, the number of pairs of legs is 

 always an uneven one. There are always one pair to each seg- 

 ment. The last pair of legs is always longer than the other 

 pairs, and this is a peculiarity of the Order. 



The digestive tube resembles that of the other Orders, but 

 the salivary glands are not long and tubular but short (Fig. 28, 

 d}. It is, moreover, not marked with constrictions corresponding 

 with the segments of the body. 



The tracheal system or the system of respiration may be 

 said to be more highly developed in this Order than in any 

 other. The tracheal branches anastomose with one another (that 

 is, the branches join), and in some cases form long tracheal stems 

 running along the body almost for its whole length. The number 

 of the tracheal openings or stigmata varies and does not correspond 

 with the number of segments. 



The nervous system differs considerably from that in the 

 Order Chilognatha ; it resembles that in the Schizotarsia, and 

 differs again from that in the other two Orders, Syinphyla and 

 Pauropoda. The brain shows some differences from other Orders 

 chiefly in the development of the different lobes which are con- 

 nected with the sense organs, the eyes and antennae, for instance ; 

 but the most marked difference is in the ventral ganglionic cord. 

 First, the ganglionic swellings are much more clearly marked 

 than in the Chilognatha. Secondly, the first three ganglia differ 



