MUSEUM OF COMPAKATIVE ZOOLOGY. 181 



Fig. 3. Covering scale of A. clegaiis (adult). 



e'. Central tube. 

 Fig. 4. Side view of the same. 

 Figs. 5, 6, 7, 8. Development of the feeding polyp of A. elegans. 



X. Structure at the base of the polypite from which arise the tentacles. 

 The region between this and the body of the polypite is homolo- 

 gous to the spherical enlargement with lasso cells shown in Fig. 8. 

 Fig. 9. Provisional tentacular knob found on the first tentacle formed in the early 



stages (AtJwnjbia and Physophora stages of A. elegans). 

 Fig. 9*. View of this knob from below. 

 Fig. 10. Taster of A. elegans. 

 Fig. 11. Young covering scale of A. elegans). 

 Fig. 12. Adult nectocalyx of the same. 

 Fig. 13. Young nectocalyx. 



Fig. 14. Primitive polypite and tentacle of Athoryhia stage. 

 Figs. 15, 16, 17. Stages in the growth of the covering scale. 

 Fig. 18. Side view of a young nectocalyx older than Fig. 13, turned a little to one end. 



a e. Mantel tube. 

 Fig. 1 9. Side view of adult nectocalyx. 

 Fig. 20. Extruded sacculus of a tentacular knob of adult. 



a. Terminal vesicle. 



b. Terminal filaments. 



c. Sacculus. 



d. Small muscles connecting two extren;ities of the sacculus. 



e. Retracted involucrum. 



Fig. 21. Tentacular knob of the adult Agalma with sacculus withdrawn into the 



involucrum. 

 Figs. 22, 22% 22S 22° 22*, 22«. Development of the adult tentacular knob up to tlie 



trifid terminal division. 

 Fig. 23. Very young covering scale. 

 Fig. 24. Termination (distal) of the taster. 

 Fig. 25. Optical section of the undeveloped covering scale of A. elegans. 



PLATE X. Agalma elegans (life size). 



j. Retracted knobs in a bundle. 



