XI 



PHYLUM ARTHROPODA 



561 



fir// 



The surface presents ;ui elaborate pattern, which varies givatlv 

 in different individuals, produced by minute mottlings of various 

 colours and tints, green, red, brown, and the arrangement of thc- 

 in stripes and bands. 



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

 of a cuticle, a layer of cleric 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 coelome 

 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 hasmoccele, and is 

 filled with blood. 



The enteric canal (Fig. 

 444) begins with a small 

 Jmccal 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 mcsentci'dii or 

 stomach-intestine, a wide, 

 somewhat thin- walled tube, 

 extends nearly to the pos- 

 terior end of the body. The 

 narrower -tret-inn, 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. 



FIG. 444. Dorsal view of the internal organs of 

 Peripatus. an. anus; n,it. antenna-; '<//< 

 brain ; cox. gld. coxal gland of the seven 

 teenth leg; $ <i<_,i. male genital aperture 

 ne. co. nerve cord; n<-ph. nephridia ; plm,- 

 pharynx ; mil. ii/J. salivary gland ; */. ///>' 

 slime gland; .s',,<. stomach. (Combined 

 from Balfour.) 



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 



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