53 



PHYSIOLOGY OF THE INVERTEBRATA. 



below by the labrum. It leads to a short and narrow oeso- 

 phagus, which ascends almost perpendicularly to the intestine, 

 in the inner cavity of which it forms a distinct maniniillar 



;^^ 



c 



projection. The walls of the oesophagus are highly muscular, 

 and its contours wavy from the strong circular muscles. 

 Besides numerous fine muscular bundles forming a continua- 



