Figs. 1-4, 7, 8, 10. Cross sections of Chaetoderma californica. (X 33.) Figs. 5, 6. Chaeto- 

 derma japonica. X 33. Fig. 9. Pronromenia hawaiiensis. 



Tlirough radula. 



Through junction of pharynx and stomach. 

 Througli heart and coelomoducts. 

 Through brain region. 

 Through brain of Chaetoderma japonica. 

 Through radida, same species. 

 Through outlet of coelomoduct, on left. 

 Pharynx and glands in front of radula. 



External sensory atrial ridge of Proneonienia hawaiiensis; os, ridge resting upon gan- 

 glion cells; om, outer atrial ridge; c, cirrus. 



Fig. 10. Thjough suprarectal commissure. 



