Figs. 1-7, 9-12. Sections of Dorymonia acuta. X 50; Fig. S. Halomenia gravida. 



Figs. 1, 2 correspond to lines .\, B indicated in fig. 7, pi. 15 (anterior end), and figs. 4, 6 lo D, C, 

 in fig. 4, pi. 6 (posterior end). 



Fig. 3. Section tlorough dorso-terminal sense organ. • 



Fig. 5. Cross section of pcnial spine. X 205. 



Fig. 7. Longitudinal section of anterior end of body. 



Fig. 8. Cross section corresponding to line D, fig. 5, pi. 3. 



Fig. 9. Cross section of young animal, posterior end. 



Fig. 10. Longitudinal section through ba.se of penial spine. X 205. 



Fig. 11. Section through dorso-terminal sense organ. X 205. 



Fig. 12. Section through atrial cavity. 



