34 



F. W. GAMBLE AND J. H. ASHWORTH. 



12. General Summary. 



The following is a recapitulation of the new points which we 

 have found in Areuicola marina, 



1. On the Lancashire coast, and probably elsewhere, two 

 well-marked varieties of Areuicola marina occur, diflferiug, 

 as the following table shows, in general appearance, in their 

 habits, in the structure of their gills, and periods of maturity. 



2. The cilia lining the central or gastric region of the 

 alimentary canal are specially arranged (1) on the sides of a 

 ventral groove which is continued to the anus, and (2) on 

 curved shallow grooves running downwards and backwards 

 into the former. The current caused by the action of these 

 cilia carries a stream of mucus and of digested food slowly 

 backwards and away from contact with the mass of sand in 

 the gut. As these grooves are in close connection with parts 

 of the visceral plexus, absorption may take place from them. 



While the ventral groove is morphologically equivalent to the 

 similar structure of Oligognathus (described by SpengeP), 

 1 "Oligouathus Bonellite," 'Mitt. Zool. Stat. Neapel,' iii, 1882. 



