434 



ARTHROPODA 



of appendas^es, a pair of several-jointed inandil>les (fig. 401). and a pair of 

 rudimentarv maxilke fused to a single plate, the giialliocliilariii))!. 



The genads lie venlral 10 die intesline far Iniek in the hody, Uiose of the right 

 and left sides enelosed in a sinL;le sae; the duets open separately on the seeond 



Fig. 400. Fie,. 401. 



Fig. 400. — Schematic section of Diplopod i,coni}xiro with fig. 4;qV t/, digestive 

 tract; 5,', gonad; h. heart; r, rcpiignatorial gland; .«, spiracle and trachea". 



Fig. 401. — }\Iouth parts of lulus (after Latzel). ;, mandibles of I. niolyhJiinis: 

 3, gnathochilarium (fused ma.viUic) of I. luriJus. 



somite of the trunk. The spermatozoa are not motile. The legs of the seventh 

 segment of the male are used in eopulation. The young escape from the egg 

 with three pairs of legs, a point once thought to show resemblances to the 

 Hexapoda, but which does not, for these legs are on the fourth, si.xth, and 

 seventh somites of the body. Iulid.e, elongate cylindrical bodies; Spiroboliisy 



Fig. 40J. — lulus iua.\iiiius vaflcr SchmardaV 

 CiLOMF.RiD.t: short, capable of rolling into a ball; PoLYPESitiD t-:. rAfROrop.\: 

 minute; body with twchc seijments, teiidiiTj; to fuse to six. I\inrof^iis/' More 

 uncertain in position are the Syiiphvi.v [Scolopcinlrclhi'''); from the position of 

 the genital opening they are placed here. 



Summary of Important Facts. 



1. The ARTHROPODA arc animals with evident internal and 

 external segmentation (metamerism). 



2. The metamerism is expressed iuternallv in the muscles, iit the lad- 

 derdike ner\-oiis system, in the structure of the heart, antl in the arrange- 

 ment of segmental organs and traclteie so far as these are present. 



