ENTEROPNEUSTA 



375 



graduallj fills the entire intestine, and finally passes out 

 tliroucrli 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 





an. 



db 



Ih 



-%}.-cf- di 



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

 sarniensis (made somewhat diagrammatic, after Köhlku). d, intestine; de, intes- 

 tinal epithelium; db, dorsal blood-vessel; di, diverticulum of the intestine; dii, 

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

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



acorn with the broad mouth-opening, which cannot be 

 closed (Fig. 1G5). It extends backwards tolerably straight. 



