60 MYRIAPODA 



CHAP. 



3 and 4. Two pairs of maxillae or foot jaws distinguished by 

 their length and slenderness. 



5. The 2^oison claius long, slender, and not sharply curved. 

 The bases of the poison claws hardly fused together and 

 short. 



The respiratory system in the Schizotarsia differs from that in 

 all other Myriapods in the fact before mentioned, that they 

 breathe by means of lungs and not by tracheae. There are, as 

 before mentioned, eight dorsal scales in these animals ; each dorsal 

 scale except the last bears one of the peculiar organs which I 

 have called lungs. At the hinder end of the scale there is a slit 

 which leads into an air sac, from which a number of short tubes 

 project into the blood in the space round the heart and serve to 

 aerate it before it enters the heart. The heart, therefore, sends 

 aerated blood to the organs, while in the tracheal-breathing 

 Myriapods the blood is aerated in the organs themselves by 

 means of tracheae. 



The poison claws are followed by segments bearing fifteen pairs 

 of true ambulatory legs. These are covered by eight large dorsal 

 plates, increasing in size from before to the middle of the body, 

 the middle plate being the largest, and then diminishing in size. 



The nervous sy stein resembles that of the Chilopoda, but there 

 is a special pair of nerves which supply the sense organ, which 

 has been mentioned as peculiar to the Order. The ventral nerve 

 cord shows a very clear division into two, the ganglia of the two 

 cords being almost entirely separate. The first few. ganglia are 

 fused, as has been mentioned in the Chilopoda. 



The digestive tube resembles that of the Chilopoda. The legs 

 ^re very long and slender, and the joints are beset with bristles. 

 Both sexes have small hook-like appendages at the sides of the 

 genital openings. 



The eyes have already been mentioned as being more highly 

 developed than in other classes, in correspondence with the more 

 active habits of the animal. The generative organs open at the 

 hind end of the body, as in Chilopoda. 



The heart is highly developed, quite as much so as the 

 Chilopod heart, the alary muscles being strong and broad, and 

 the arteries being quite as perfect as those in any Myriapod. 

 The muscular coats which govern the pulsations by their con- 

 tractions are powerful and well developed. 



