PLATE XI. 



Fig. I. Amphiporus nebulo$us. Transverse section through posterior portion of 

 ventral commissure of brain. The submuscular glands i^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. 83. (X 26). 



2. Amfhiporus 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 (/«) 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 («c/) are seen. Submuscular glands {s7ng) are not as 

 numerous as in A. nebulosus. Other reference letters as above. (X 26). 



3. Amfhiforus 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. (X32)- 



(106) 



