EXPLANATION OF PLATES. 



PLATE I. 



Figs. 1 to 6. Halomolgula ovoidia. 



Fig. 1. Whole animal, natural size a rather large specimen. 



Fig. 2. Surface view of the test surrounding the branchial orifice, show- 

 ing the arrangement of the papillae. 



Fig. 3. A few of the papillae, considerably enlarged. 

 Fig. 4. A tentacle of the first order. 



Fig. 5. The ganglion, hypophysis, and meandering course of the periphar- 

 yngeal band, dorsal view. 



Fig. 6. One side of a branchial fold. Some of the stigmata are more 

 elongate and curved than any shown in this figure. 



Figs. 7 and 8. Molgula re</iilurit<. 



Fig. 7. Lateral view of the animal removed from the test. X-. 

 Fig. 8. Ganglion and surrounding parts seen from inside the branchial 

 sac. 



Figs. 9 to 16. Halocynthia olai. 



Fig. 9. Whole animal, natural size. 



Fig. 10. Branchial orifice, X 2. 



Fig. 11. One of the large spines, X 3. 



Fig. 12. A smaller spine without terminal whorl of spinelets, X 3. 



Fig. 13. Two of the short whorled spines, X 42. 



Fig. 14. A single tentacle. 



Fig. 15. Small portion of the branchial membrane, inner surface. 



Fig. 16. Scheme of a section of a branchial fold. 



MS | 



