ENTEROPNEUSTA 



375 



gradually fills the entire intestine, and finally passes out 

 through the anus at the posterior end of the body as a 

 sausage-like cord. Thus the animal eats its way, as it were, 

 through the sand. 



The intestinal canal commences immediately under the 



Fig. 165. — Sagittal section through the acorn and collar of BnlanogJossus 



imiensis (made somewhat diagrammatic, after Kohlkr). d, intestine; de, intes- 



inal epithelium ; db, dorsal blood-vessel ; di, diverticulum of the intestine ; dn, 



dorsal nerve ; h, the so-called heart; Ih, the body cavity; m, mouth ; p, proboscis 



pore; sk, skeletal body; vh, ventral blood-vessel; x, the so-called proboscis gland. 



acorn with the broad mouth-opening, which cannot be 

 closed (Fig. 165). It extends backwards tolerably straight. 



