PLATE 9. 



PLUMATELLA VITREA Hyatt. 



Fig. 1 . Enlarged view of five groups on one branch, corresponding to 

 the first five on the left of the branch below, fig. 2. (Cambridge, Mass.) 

 Fig. 2. View of one branch, natural size. 



Fig. 3. Shows the great extent to which the polypide is often evagi- 

 nated. D, ectocyst; E, endocyst ; B, invaginated fold ; K', stomach. 



PECTINATELLA MAGNIFICA Leidy. 



Fig. 4. Outline of a mass gathered on the stump of a dead branch. 

 (Norway, Me.) The outline of the branch where it is covered by the mass, 

 is indicated by a dotted line. This figure shows the general aspect of the 

 mass, the great thickness of the ectocyst, and the general arrangement of 

 the colonies. A, outlines of coencecia ; D, ectocyst. 



Fig. 5. The outline of a colony, natural size, from a large mass, show- 

 ing the radiating and tripartite character of the lobes. A ', coenoecial trunk ; 

 A", coenoesial lobes, divided into three minor lobes. 



Fig. 6. Ideal transverse section of the same, with the polypides ex- 

 panded. W, statoblasts ; A ', coenoecial trunk ; C, polypide. 



Fig. 7. The colony represented in the outline of fig. 5, after being 

 treated with alcohol. C ', dead and retracted polypides ; A ', coenoecial 

 trunk ; A ", coenoecial lobes ; W, statoblasts. 



Fig. 8. Younger colony, showing the central polypide. 



Fig. 9. Young colony, showing the genesis of five polypides, the pro- 

 genitors of an equal number of branches, from tjhe central polypide. 



Fig. 10. A young colony enlarged, showing the arrangement of the 

 polypides. (Cambridge, Mass.) 



Fig. 11. A very old colony; the coenoecial trunk occupied by numer- 

 ous statoblasts, and the half absorbed remains of dead polypides. W, 

 statoblasts ; C ', dead polypides. 



Fig. 12. Ventral view of a closely retracted polypide, showing the 

 positions and relations of the three pairs of retractors. (Norway, Me.) K ', 

 bottom of the stomach ; K, part of the oesophagus ; M, gastric retractors ; 

 M ', lophophoric retractors ; M ", brachial retractors ; N, anterior retentors. 



Fig. 13. Lateral view of a retracted polypide, showing the aspect of 

 the fourth membrane and of the retractors during the process of imagina- 

 tion. J "", fourth membrane of the alimentary canal ; M, gastric retrac- 

 tors ; M ", brachial retractors ; V, funiculus ; K, oesophagus ; K', stomach; 

 K", intestine ; I, lophophore ; H, tentacles. 



CRISTATELLA OPHIDIOIDEA Hyatt. 



Fig. 14. View from above of the lophophore of an immature polypide. 

 The arms are still joined near the extremities, and the tentacles and calyx 

 along the line of the juncture remain undeveloped. (Norway, Me.) 



