BY S. J. JOHNSTON. 115 



EXPLANATION OF PLATES. 



Plate V. 

 Hemistomiun trlangulare (figs. 1-6). 

 Fig. L — Whole view of mounted animal ( x 50). 



Fig. 2.— Longitudinal section, about the middle line in most of its length, 

 but posteriorly to one side of the middle line through a slight 

 lateral flexure in the body ( x 70). 

 Fig. .3. — Section through posterior end showing bursa and genital papilla, 



&c. ( X 70). 

 Fig, 4. — Longitudinal section showing group of unicellular glands surround- 

 ing ventral sucker ( x 420). 

 Fig. 5.— Transverse section through anterior body-region showing flexed 



lateral edges of body. 

 Fig. 6. — Sketch of an unmounted specimen; side view ( x 20). 



Hemistomum intermedium (figs. 7-10). 

 Fig. 7.— Longitudinal section a little to one side of the middle line, showing 



stalked ventral sucker and characters of clinging plug and 



uterine wall ( x 37). 

 Fig. 8. — View of whole animal, mounted ( x 20). 

 Fig. 9. — Longitudinal section through the posterior end ( x .37). 

 Fig. 10. — Slanting section through the two anterior groups of glands ( x 37). 



Plate vi. 

 Holostomum Hillii (figs. 1-8). 



Fig. 1. — Drawing of whole animal, mounted ( x 20). The amount of dorsal 

 flexure shown is about the usual amount shown in this species. 



Fig. 2. — Longitudinal section through the anterior body-region, showing the 

 separate dorsal and ventral walls of the clinging plug ( x 50). 



Fig. 3. — Transverse section through the anterior body-region, showing the 

 commencing separation of the ventral wall of plug ( x 50). 



Fig. 4. — Transverse section further forward than fig. 3, showing the separa- 

 tion of the ventral wall still further advanced ( x 50). 



Fig. 5. — Transverse section still further forward, and showing the ventral 

 wall of plug completely separated from the wall of the cup; this 

 section passes through the fused part of the two lateral portions 

 of this ventral wall ( x 50). 



Fig. 6. — Transverse section through posterior body-region ( x 50). 



Fig. 7. — Longitudinal section through posterior body-region and bursa 

 copulatrix ( x 35). 



Fig. 8. — Transverse section through bursa and genital papilla in front of the 

 junction of the two genital ducts ( x 37). 



