PLATE XI. 



Fig. i. Amphiporus nebulosus. Transverse section through posterior portion of 

 ventral commissure of brain. The submuscular glands (smg) fill up 

 a large portion of the tissues of the ventral half of the head. The 

 pair of nerves leading forward to the cerebral sense organs is seen to 

 originate (son) from the ventral side of the dorsal ganglia. Other 

 reference letters are explained on p. S3. (X 2 ^). 



2. Atnphiporus angulatus. Transverse section through ventral commis- 

 sure of brain. The dorsal attachment of the proboscis to the tissues of 

 the head is shown. The proboscis nerves (pn) enter the ventral side of 

 the proboscis, and divide into a definite number of branches (usually 

 18), which farther back arrange themselves symmetrically about the 

 periphery. The roots of the dorsal brain commissure (rdc) are indi- 

 cated. In the right half of the section the anterior ends of the nephri- 

 dial tubules [nep~) are seen. Submuscular glands {smg) are not as 

 numerous as in A. nebulosus. Other reference letters as above. (X 2 )-' 



3. Amphiporus exilis. Transverse section through nephridial region to show 

 efferent nephridial ducts (nep) opening on dorso-lateral aspects of body. 

 This condition is extremely rare in Metanemerteans. Several diverti- 

 cula of the intestinal caecum (inc) are represented. Other reference 

 letters as above. (X3 2 )- 



(106) 



