806 



ZOOLOGY. 



and Europe, which may be called Antliracarida, and 

 which have antennae and tails like shrimps, but the body 



Fig. 254. Gampsonyx fimto'iatits of European coal 

 eize. 



m 



times natural 



and limbs like Amphipods. In the Isopods the body is flat- 

 tened and the head rather broad. 



Fig. 256 is a dorsal view of Serolis Gau- 

 dicTiaudi Audouin and Edwards, with the 

 two pairs of antennae and pointed sides of 

 each thoracic segment, dissected to show the 

 nervous system, the two pairs of antenna! 

 nerves ; the optic nerves (op) sent to the 

 compound eyes. Fig. 257 represents a trans- 

 verse section of the body, showing the mode 

 of insertion of the legs, and the equality in 

 the tergal and sternal sides of the body. 

 Fig. 259 represents a gill. In the common 

 pill-bug (Porcettio) aerial respiration is per- 

 formed by respiratory cavities situated in 

 the abdomen. In Tylos similar cavities are 

 filled with a multitude of branching co3ca, 

 serving for aerial respiration, thus antici- 

 pating the tracheary system of insects. 

 The nervous system is quite simple. (Fig. 

 255, Idotwa, and Fig. 256, that of Serolis.) 

 The digestive canal is straight, consisting 

 . 255. Nervous of a short oesophagus, a membranous stoin- 

 Drawn B by*jT ach, and usually a short tubular intestine ; 

 the liver consisting of several short coeca. 

 In Serolis Gaudichaudi the stomach is somewhat pear- 



