372 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
EXPLANATION OF PLATES. 
Figures la, 16, are from photographs by Dr. A. M. Reese; figures 2 to 13 were drawn by Mr. C. Id. 
Prinke under the supervision of the author; all the others were drawn by the author. 
Plate I. 
Figs, la, 16. Stoichactis helianthus. Photographic reproductions of two preserved polyps, showing the 
differences in character which may be assumed by the tentacles. 
Plate II. 
Fig. 
2. 
Fig. 
3. 
Fig. 
4. 
Fig. 
5. 
Fig. 
6. 
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7. 
Fig. 
8. 
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9. 
Fig. 
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11 . 
Fig. 
12. 
Fig. 
13. 
Fig. 
14. 
Fig. 
15. 
Fig. 
16. 
Fig. 17. 
Fig. 18. 
Fig. 19. 
Zoanthus pulchellus. A colony of retracted preserved polyps in which the individuals are long 
and close, and hide the ccenenchyme. 
Zoanthus pulchellus. Portion of a preserved colony in which the polyps are shorter, and the 
intervening continuous coenenchyme is partly displayed. 
Zoanthus sociatus. Portion of a colony of retracted polyps. 
Isaurus duchassaingi. Retracted polyp. 
Protopalythoa vanabilis. A small irregular group of retracted polyps. 
Palythoa caribxa. A small colony of partly expanded polyps. 
Asteractis expanse,. Polyp as seen expanded in a narrow glass vessel. 
Bunodosoma gramdifera. Living expanded polyp. 
Plate III. 
Bunodosoma sphefidata. Enlarged preserved polyp. 
Ai/>tasia anniduta. Living expanded polyp. 
Calliactis tricolor. Living expanded polyp. 
Phymanthus crucifer. Living expanded polyp. 
Plate IV. 
Zoanthus pulchellus. Vertical section through the upper part of the column-wall, displaying 
the double mesogloeal sphincter muscle. Other details are omitted. 
Zoanthus sociatus. Vertical section through the upper part of the column-wall, displaying only 
the double mesogloeal sphincter muscle. 
Transverse section through the stomodaeal region of a polyp in which the mesenteries are 
brachytypic on the left side and macrotypieon the right. At the slight magnification given 
only the outlines of the mesenteries could be indicated. 
Plate V. 
i 
Zoanthus sociatus. Thick longitudinal section through the lower part of (he stomodaeal wal 
and along the edge of a complete mesentery. The stomoda-al ectoderm is seen to lie in 
continuity with the mesenterial filament along the free edge of the mesentery; the ciliated 
bands are removed a slight distance from the actual mesenterial border and are seen to be 
sinuous in sections, the appearance varying in different regions according to the actual 
direction of the section. 
Transverse section through the free edge of a mesentery a little below the level of the 
stomodfeum. The intermediate streak (bit. st.) of the mesenterial filament is seen on both 
sides asa thick layer separating the median glandular streak (gl. st.) from the ciliated band 
( cil . bd.); in this particular section the latter is almost covered by the endodennal-like 
tissues of the intermediate streak. 
Transverse section through the mesenterial filament immediately below the stomodfeum. 
Histologically the tip of the filament very closely resembles the stomodfeal ectoderm; the 
ciliated band (reflected ectoderm) is continued a< two wings to the filament, and on the 
right side is in continuity with the tissue at the tip, while on the left side the continuity is 
interrupted by the presence of the intermediate tissue. 
