104 NATURAL HISTORY OP OUR SHORES 



of some similarity in their development and the presence 

 in some of their genera of a trace of segmentation. 



A curious feature in their anatomy is, that the alimentary 

 canal, which is several times the length of the body, is folded 

 to and fro in its length, and then turned into spiral form, 

 like a looselv twisted skein of twine. 



