EXPLANATION OF THE PLATES. 



(19) 



covered with lasso-beariug papilloe at tlie base. In 

 segments 4 and 6 another arm is visible witli its marginal 

 lobes and papillaj removed, in order to show that the 

 arms have the same structure in the Discophorie Rhi- 

 zostomete as in the Semajostomea;, only that their margin 

 is soldered in the Rhizostomea;, having only narrow 

 openings for the admission of the food, instead of 

 forming open channels. In segments 7 and 8 the base 

 of the arm, with its papilla; m, is alone preserved. 

 In segments 10 and 11, and parts of 9 and 12, the 

 base of the oral appendages is removed to show the 

 main cavity of the body c c. In segments ij' and 7 

 the ramifications of the chjuiiferous tubes are repre- 

 sented as they appear through the lower lloor when 

 injected. In segments 8, 9, 10, 11, and 12 dilferent 

 aspects of the lower surface of the lower floor are 

 rejiresented ; iu segments 1 1 and 1 2 from a spei.-imen 

 in which it was almost smooth ; in segments 9 and 

 10, with various folds, concentric near the margin, 

 convolute further inward, and pennate between the 

 principal chymiferous tubes. In segment 8 the same 

 arrangement prevails, but differently combined. 



Fig. 3. Young specimen of Polyclonia frondosa seen 

 from below. o eyes ; t arms or oral appendages. 



Fig. 4. Internal view of the main cavity with the four 

 sexual pouches o os oa. o sexual organ susjjended 

 between the folds os of the sexual pouches ; oa openings 

 of the sexual pouches, alternating with the arms t f, 

 ;' /', /- t-, 1^ t^- s openings of the channels of the four 

 arms into the main cavity. 



Fig. 5. Central cavity seen from below, with a few 

 chymiferous tubes radiating from one of its corners. 



Figs. 6 and 7. Openings of the channels leading into 

 the main cavity. 



Figs. 8, 9, 10, 11, 12, i:>, and 14. Various kinds of lasso- 

 beai'ing papill;v, /, from the base of the arms. 



Figs. 1.5 and IG. Lobes of the margin of the arms with 

 their fringes t, to show the openings s, leading into 

 tlie main channel of the oral appendages. 



Fig. 17. Lasso-cells. 



Plate XIIP. Side view of Polyclonia frondosa, with 

 various structural details. 



Fig. 1. Profile view of Polyclonia, with the disk some- 

 what raised in front to show the opening of a sexual 

 pouch between two arms. 



Fig. 2. Transverse section of the disk. 



Fig. 3. Portion of the same, magnified, r; upper tloor; 

 a' layer of the chymiferous tubes ; o lower floor. 



Fig. 4. Portion of an arm, seen from its outer side, with 

 the marginal lobes and fringes extended. 

 VOL. III. 41 



Fig. 5. The same, from the inner side. s channels 

 leading into the main cavity ; (/ marginal lobes and 

 fringes ; rf' papilla; of the base of the arm. 



Fig. 6. View of the disk from above. 



Fig. 7. Segment of the same, in which the colored ring 

 is not divided into several zones as in fig. 6. 



Fig. 8. Portion of the margin, with two eyes, o' o\ in 

 the same spheromere. 



Fig. 9. Magnified portion of the margin, showing the 

 anastomoses of the chymiferous tubes «'. 



Figs. 10, 11, and 12. Margin of the disk, to show how 

 the edge is thinned out into a sort of veil, beyond 

 the marginal lobules, between which the eyes, o (figs. 

 11 and 12), are situated. 



Figs. 13, 14, and 15. Eyes. 



Figs. IG, 17, 18, 19, 20, 21, and 22. Eggs in various 

 stages of development. 



Fig. 23. Spermatic particles. 



PLATE XIV. 



Stomolophus Meleagris, Ay. 

 [Drawn from nature by A. Sourel and J. Burckhardt.] 



Fig. 1. Profile view of Stomolophus Meleagris. 



Fig. 2. Profile view of the oral appendages, presenting 

 two rows of prominent crests, the upper of which is 

 concealed under the disk in their natural position. 



Fig. 3. Transverse section across the upper part of the 

 oral appendages, just below the main cavity. 



Fig. 4. View of the oral appendages from below. The 

 letters and figures in figs. 2, 3, and 4 correspond to 

 one another. 



Fig. 5. (Jne of the crests of the upper row seen side- 

 ways. 



Fig. 6. The same, its two halves being separated. 



Fi"-. 7. One of the crests of the loweu row seen side- 



ways 



Fin-. 8. The end of the same seen from above. 



PLATE XV. 

 Pennaria gibbosa Ag., Millepoba alcicornis Linn., 



POCILLOPORA D.^MICORNIS Lmk., SERIATOPOR.'i^ Sl- 

 BUL.\T.\ Lml. 



[Figs. 1, la, 2, 9, 10, 11, 12, 13, 14, 14a, 15, and 15a drawn from 

 natvire by A. Sonrel; tigs. 4, 5, 5a, 5b, 5c, 6, 7, ami 8 by H. 

 J. Clark, from sketches by L. Agassiz and the help of alco- 

 holic siiecimens; fig. 3 by .1. Burckhardt.] 



Millcpora, Pocillopora, and Seriatopora were thus far re- 

 ferred to the Polyps. 



