Plate XXI. 



Tbistomum sinuatum. 



Fig. 1. Median sagittal section of the anterior part of the body, x 73 diam. 



„ 2. A small lateral portion of a horizontal section of the body ; to show the 

 marginal sticky glands and their ducts, x 204 diam. 



„ 3. A small lateral portion of a cross-section of the body ; to show the open- 

 ing of the marginal sticky glands, x 204 diam. 



„ 4. A small ventral portion of a cross-section of the body, x 204 diam. 



„ 5. A portion of a horizontal section of the body just behind the pharynx. 

 X 204 diam. 



„ 6. Cross-section of the oviduct at the point of its junction with the ootyp ; to 

 show the opening of the shell-glands, x 204 diam. 



„ 7. Beginning of the yolk-duct, x 427 diam. 



„ 8. Principal part of the female genital organs viewed as a transparent object 

 from the ventral side, x 44 diam. 



