ENTEROPNEUSTA 



375 



gradually fills the entire intestine, and finally passes out 

 through the anus at the postei'ior end of the body as a 

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

 through the sand. 



The intestinal canal commences immediately under the 



ai 



^K- 



V.L 



de 



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

 sarniemis (made somewhat diagrammatic, after Kohler). d, intestine ; Ae, intes- 

 tinal epithelium; Ah, dorsal blood-vessel; Ai, diverticulum of the intestine; An, 

 dorsal nerve ; li, the so-called heart ; lli, the body cavity ; m, mouth ; ]), 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. 



