400 



ARTHROrODA 



The description may he completed by saying; that tlie straight alimentary 

 canal ij> and d) bears oniv salivary glands (sp) ; that it is accompanied throughout 

 by a dorsal heart; that the gonads (the sexes are separate) open just in front of 

 the anus i^c), their ducts being modified nephridia. The animals are vivipar- 

 ous, li\e in decaving wood, hide by day and hunt their prey at night. The 

 several species have a wide but discontinuous distribution (South America, Cape 

 of Good Hope, New Zealand, etc.), an indication of great antiquity. Recently 

 the forms ha\e been dixided into se\eral genera, Pfripaliis. Pcn'palopsis, 

 Opislhopalus, etc. 



Fig. 436. — Anatomy of female Fcn'palns opened dorsally (from figures of Afosoloy 

 and Balfour), a, anus; al, antenna'; bin, ventral nerve cords; (/, digestive tract; go, 

 genital opening; 0, ovary; og, brain; p, pharyn.x; sJ, slime gland; so, nephridia; sp, 

 salivary gland; Ir, traehex; 11, uterus. 



Class IV. Insecta. 



The Insecta is a disliiict group marked off from all otl\er arthropods 

 by several important characters. The appendages show no signs of a 

 schizopodal condition. The head is always a distinct region, bearing a 

 single pair of antenna\ a pair of mandibles, and two pairs of maxilkv, the 

 posterior pair often being fused into a lower lip or labium. 



