482 INVERTEBRATE MORPHOLOGY. 



the fusion of certain metameres in pairs, so that two pairs of 

 appendages appear to belong to some of the segments, the 



double nature of which is further shown by 

 the occurrence in them of two pairs of 

 nerve-ganglia. The antennae (Fig. 221) are 

 remarkable in form, consisting of a four- 

 jointed basal portion which bifurcates at 

 the tip, one of the bifurcations bearing two 

 long flagella and a peculiar spherical 

 stalked body, while the other one bears a 

 single flagellum. Mandibles are present, 

 and there is also a single pair of but poorly- 

 developed maxillae. 

 FIG. 221. Pauropus Tracheae or other respiratory organs are 

 Huxieyi (from I.KUIII&). not yet known to exist. A large simple eye 

 occurs on each side of the head near the 

 base of the antennae, and the reproductive opening is situa- 

 ted upon the second trunk-segment. 



Further study of this group is much needed to elucidate 

 its characteristics. The genus Pauropus has ten trunk-seg- 

 ments, of which the first nine bear appendages ; while in 

 Eurypauropus there are only six trunk-segments, and eyes are 

 wanting. 



2. Order Diplopoda. 



The Diplopoda, sometimes termed the Chilognatha, are 

 popularly known as the Millipedes on account of the commoner 

 forms possessing an unusually large number of appendages. 

 The body is usually cylindrical and provided with a hard 

 cuticle, and many forms are in the habit of rolling themselves 

 when disturbed into a ball or a helixlike coil, thus protect- 

 ing the more delicate ventral surface of the bod}\ The an- 

 tennae (Fig. 222, at] are generally seven-jointed and are never 

 very long, and the mandibles are strong jaws without palps. 

 In front of the mouth is a well-developed upper lip (id), while 

 behind it is a lower lip formed by a fusion of the maxillae (ma;). 

 According to some authors this lower lip represents two pairs 

 of appendages, but its iunervation and embryological history 

 seem to be opposed to this view. The segments behind the 



