52 



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 mammillar 



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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 continiiS'* | 



