PHYLUM ARTHROPODA 



561 



cm* 



Lrn 



The surface presents an elaborate pattern, which varies greatly 

 in different individuals, produced by minute mottlings of various 

 colours and tints, green, red, brown, and the arrangement of these 

 in stripes and bands. 



Body wall and body cavity. The wall of the body consists 

 of a cuticle, a layer of deric epithelium with an underlying 

 layer of fine fibres, a layer 

 of circularly arranged muscu- 

 lar fibres, a double layer of 

 diagonal fibres, and a layer 

 of longitudinal fibres divided 

 into a series of bundles. A 

 layer of ccelomic epithelium 

 lines the wall of the ccelome 

 and invests the contained 

 organs. Incomplete muscular 

 partitions divide the cavity 

 into a median and two lateral 

 compartments. As in the Ar- 

 thropoda in general, the body- 

 cavity is a hsemoccele, and is 

 filled with blood. 



The enteric canal (Fig. 

 444) begins with a small 

 Imecal cavity enclosed by the 

 circular lip, and having on 

 its floor a slight prominence, 

 the tongue. This is followed 

 by a thick-walled pharynx 

 (phar.) leading to a narrow 

 oesophagus. The part which 

 follows, the mesenteron or 

 stomach-intestine, a wide, 

 somewhat thin-walled tube, 

 extends nearly to the pos- 

 terior end of the body. The 

 narrower rectum leads to an 

 anal aperture situated on the 

 last segment of the body. 

 A diverticulum leading back- 

 wards from the buccal cavity, 

 receives the secretion of two 

 long narrow tubular salivary 

 glands (sal. gld.). 



Circulatory system. The heart is an elongated tube run- 

 ning through nearly the entire length of the body. It presents a 

 number of pairs of ostia arranged segmentally i.e. one opposite 



VOL. i o o 



- O f/ff 



FIG. 444. Dorsal view of the internal organs of 

 Peripatus. an. anus ; ant. antennae ; brn. 

 brain ; cox. gld. coxal gland of the seven- 

 teenth leg ; $ gen. male genital aperture ; 

 ne. co. nerve cord ; neph. nephridia ; phar. 

 pharynx ; sal. gld. salivary gland ; si. gld. 

 slime gland ; atom, stomach. (Combined 

 from Balfour.) 





