484 INVERTEBRATE MORPHOLOOT. 



pairs of ganglia. Eyes are usually present and are always 

 simple, varying in number from two to as many as eighty. 



The Diplopoda are bisexual, and the ovaries or testes form 

 a single mass from which two ducts, or one which later 

 divides into two, arise and pass forward to open on the ven- 

 tral surface of the body between the second and third trunk- 

 segments. The embrj'os when first hatched out possess but 

 three pairs of legs, situated upon the first, third, and fourth 

 segments in Strongylosoma, and on the first, second, and fourth 

 in lulus, one or more segments without appendages lying 

 behind the fourth pair. By successive moults new segments 

 and appendages are added and the form of the adult gradu- 

 ally acquired. 



The Diplopoda live for the most part under stones, etc., 

 or among dead leaves, and find their food in decaying vege- 

 table matter, though some forms will attack living vegetation 

 and may prove thereby injurious to gardens. The commonest 

 form, lulus, may readily be obtained under stones or boards 

 all through the summer. 



3. Order Chilopoda. 



The Chilopoda, or Centipedes, are very different in their 

 habits from the Millipedes, being carnivorous and provided 

 with poison-glands which render the larger forms of Scolo- 

 pendra dangerous even to man. The body is as a rule some- 

 what flattened and less hard than that of the Diplopoda. 

 The antennae (Fig. 223, at) are usually long, with at least 

 twelve joints, and may be as long as the body, while the 

 mouth-parts are much more complicated than in the Dip- 

 lopoda. The mandibles and upper lip resemble the corre- 

 sponding parts in that group, but the masillse (mx) are jaw- 

 like, are not fused together, and in some forms {Geopliilm) 

 bear a palp. Behind the maxillae comes a pair of second 

 maxillBB (mx'), which, however, do not serve as jaws but are 

 reduced to a pair of palplike structures, and behind these again 

 is a pair of maxillipeds (mxp), the appendages of the first 

 trunk-segment, with their basal joints fused to form a lower 

 lip supporting a four-jointed palp, the last joint of which is 



