592 



ZOOLOGY 



SECT. 



colours and tints, green, red, and 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 circular muscular fibres, and one of 

 longitudinal muscular fibres divided into a series of bundles. A 

 layer of epithelium lines the wall of the body-cavity and invests 

 the contained organs. Incomplete muscular partitions divide the 

 cavity into a median and two lateral compartments, in addition to 

 the pericardium, or space in which the heart is lodged ; the lateral 

 compartments send prolongations into the legs. The body-cavity 



is not a coelome, 

 but, as shown by 

 its development, a 

 haemoccele an ex- 

 tension of the blood- 

 vascular system 

 as in the Crustacea. 

 The enteric 

 canal (Fig. 488) 

 begins with a small 

 buccal cavity, formed 

 secondarily by the 

 union of a ring of 

 papillae and folds 

 surrounding the 

 true mouth into a 

 circular lip : it en- 

 closes the bases of 

 the jaws and bears 

 on its roof a slight 

 prominence, the 



Fia. 487. Ventral view of head of Peripatus (Peripatopsis) ton 9 ue > ^ ltn . a rOW 

 capensis, with antenna?, jaws, oral papillae, and first pair OI small Spines Or 

 of legs. (After Balfour.) teeth. 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 

 posterior end of the body. The narrower rectum leads to an anal 

 aperture situated on the last segment of the body. A diverticulum 

 leading backwards from the buccal cavity, where it passes into the 

 pharynx, receives the secretion of two long, narrow, tubular salivary 

 glands (sal. gld.). 



Circulatory system. The heart is an elongated tube running 

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

 number of pairs of valvular ostia arranged segmentally i.e., one 

 opposite each pair of legs. It is enclosed in a pericardial sinus 



