PLATE 6. 



Entire animal of Nierstrassia fragile. X 13. 



Hypodermal layer. X 800. 



Reconstruction of anterior end of body. 



Section through posterior end of body along hne F of fig. 5. 



Reconstruction of posterior end of body. 



Section through posterior end of body along line C of fig. 5. 



Same along line D of fig. 5. 



Section through region of brain along line A of fig. 3. 



Longitudinal section through brain and anterior end of alimentary canal. X 180. 



Section through posterior end of body along line E of fig. 5. 



Posterior end of body, ventral view. 



