29 



body better than any description. The invaginated body 

 wall between a and d forms both the proboscis, which 

 can be protruded, and a proboscis sheath; part of the 

 latter, however, can be everted (fig. b to c). 



4 



Fig. 4. 



The section of the proboscis sheath a- b in Text-fig. 4 

 is connected somewhat closely to the body wall by short 

 muscles. This region retains its position whatever be the 

 disposition of the proboscis. A definite ring of muscle 

 and connective tissue (usually of a reddish hue in fresh 

 specimens) encircles the sheath at b, and marks the 

 boundary of the next section b-c. This portion, about 



