428 



COMPARATIVE ANATOMY 



CHAP. 



with transverse rows of papillae, which give it a ringed appearance, 

 and each falls into two parts, a larger proximal conical leg and a 

 smaller, narrower, distal foot, ending in two chitinous claws. 



Integument. The body epithelium (hypodermis) is externally 

 covered by a delicate chitinous cuticle. The spines on the papillae and 

 claws on the feet also belong to the cuticular formation secreted by the 

 hypodermis. Under the hypodermis lies a peculiar subepithelial layer, 

 formed of fibres running in various directions. 



Musculature (Fig. 291). Peripatus has a strongly developed dermo- 

 muscular tube, which consists of the following layers : (1) an external 

 layer of circular muscular fibres ; (2) a double layer of fibres crossing 

 each other diagonally; (3) internally a strong longitudinal layer, con- 



t/m 



rt 



FIG. 291. Transverse section through the antepenultimate segment of a female Peri- 

 patus Edwardsii (after Gaffron). n, Longitudinal trunks of the nervous system ; h, heart (con- 

 tractile dorsal vessel) ; 7m, longitudinal muscles ; ut, uterus ; d, intestine ; on, outer apertures of 

 the nephridia. 



sisting of various bundles, whose arrangement on a transverse section 

 of the body is shown in Fig. 291. In addition to these layers there 

 are numerous sagittal or transverse muscle fibres corresponding with 

 the dorso-ventral or transverse muscle fibres of the Annulata. Some 

 of these fibres run through the body cavity in such a way as to divide - 

 it into a median and two lateral divisions, the former containing the 

 heart, the intestine, and the sexual organs, the latter the longitudinal 

 trunks of the nervous system and the segmental organs. The muscul- 

 ature of the extremities chiefly proceeds from the layer of diagonal 

 fibres and the sagittal musculature. Special muscles serve for moving 

 the jaws, claws, etc. 



None of the muscle fibres of Peripatus, except those of the 

 jaw muscles, 1 are transversely striated. 



The alimentary canal runs nearly straight through the body. 



1 This exception, however, does not hold good for P. Leuckartii. 



