PLATE VI. 



Fig. 1. Young Velella seen in profile, measuring about j\ of an inch in length: c, central chamber; 



I, central part of the liver in the conical part of the iloat; /, flexible keel formed by the free 



edge of the mantle; cp, central feeding polypite; t, prehensile tentacles; /jj, small feeding 



polypites. 

 Fig. 2. Same seen from the lower side, with single ramifications of the liver system extending to the 



edge of the horizontal mantle. . 

 Fig. 3. Somewhat younger than the precejiing stage. The ramifications of the liver system are less 



pronounced ; the central feeding polypite is not expanded as in the other stages. 

 Fig. 4. One of the large blue prehensile marginal tentacles, t, of the preceding figure. 

 Figs. 5, 6, 7. Different stages of growth of the small feeding polypites of Fig. 3. 

 Fig. 8. Smallest Velella found at the Tortugas, with a hood-like free mantle, with only four chambers, 



a conical float, much like that of PL III, Fig. 1, in shape, surmounted by a flexible flat ellip- 

 tical crest, with a large central polypite, eight large prehensile marginal tentacles, and the 



same number of small rudimentary feeding polypites. 

 Fie. 9. The same as Fig. 8, seen from above, showing the simple tubes of the liver system of that stage. 

 Fig. 10. Central polypite of a large Velella slightly drawn in. 

 Fig. 11. Difterent attitude of the same. 

 Fig. 12. Basal part of the same when fully expanded. 

 Fig. 13. Distal extremity of the same when fully extended. 

 Fig. 14. Terminal part of one of the prehensile tentacles, showing the band of lasso-cells running along 



the edges. 

 Fig. 15. Somewhat more magnified view of a part of such a tentacle, sho^ving the terminal band of 



lasso-cells. 

 Fig. 16. Part of the base of a prehensile tentacle where the band of lasso-cells becomes broken up in 



patches. 

 Fig. 17. One of the prehensile tentacles showing the passage of the terminal band of lasso-cells into 



patches near the base. 

 Fig. 18. Young prehensile tentacle, with lai^e patches of lasso-cells, but without a terminal band. 

 Fig. 19. Portion of proliferous polypite with young medusae buds to, and the extremity of the tubule t. 

 Figs. 20, 21. Ramifications of the vascular system at the base of the feeding polypites on the mantle of 



the lower side of the float. 

 Fig. 22. Enlarged view of the central feeding polypite of an adult Velella, showing the rudimentary lips 



of the actinal opening and the longitudinal rows of patches of lasso-cells 6. 



