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xiv LIST OF THE WOOD-CUTS. 



Fig. 319. One of the tentacles, seen in profile 190 



" 320. Profile of ECTOPLEURA OCHRACEA, magnified 191 



" 321. The same, seen from the abactinal pole . . . . . . .192 



" 322. The same, seen from the actinal pole . . . . . . . . 192 



" 323. The base of one of the tentacles, magnified . . . . . . . .192 



" 324. Medusa of CORYMORPHA PENDULA, seen in profile. (H.J.Clark.) . . 193 



" 325. Single Hydra of HYBOCODON PROLIFER. (L. Agassiz.) 193 



326. Ilybocodon prolifer, seen from the broad side. (L. Agassiz.) . . . . 194 



327. Hybocodon prolifer, seen facing the long tentacle. (L. Agassiz.) . . .194 



328. Medusa bud of Ilybocodon prolifer. (L. Agassiz.) 194. 



" 329. Part of male community of HYDRACTINIA POLYCLINA. (L. Agassiz.) . . 198 



" 330. Part of female community. (L. Agassiz.) ....... 198 



" 331. Oil-float of NANOMIA CARA, magnified 200 



" 332. Nanomia cara, natural size 201 



" 333. Swimming-bell of Nanomia cara, seen facing the side of the straight chymiferous 



tubps 202 



" 334. The same bell, from the actinal pole 202 



335. Portion of the same bell, seen from the abactinal pole 202 



336. Same bell as Fig. 333, seen from the other side 203 



337. Group of swimming-bells in different stages of development . . ... 203 



338. Cluster of Medusas (Polyps) of first kind formed, with knob-shaped tentacles . 204 

 " 339. Enlarged view of the knob of a tentacle of the first kind of Medusas . . 205 

 " 340. Second kind of Medusas, with cork-shaped tentacles ...... 205 



" 341. Third kind of Medusa, having a single thread-like tentacle .... 205 



" 342. Cluster of Medusas (Polyps), in different stages of development, before the ap- 

 pearance of the scale and of the tentacles ....... 206 



" 343. Knobs like those of Fig. 339, in different stages of development . . . 207 



" 344. Same kind of knob, still further developed . . . . . . . .207 



" 345. Young scale, seen from different sides ........ 207 



" 346. Youngest Nanomia found swimming on surface ....... 208 



" 347. Somewhat more advanced .......... 208 



" 348. The terminal Hydra is open, tentacles are developed as well as clusters of small 



swimming-bells ........... 209 



" 349. Still more advanced Nanomia 209 



" 350. Young Nanomia, where we find several Medusas of the first kind . . . 209 



" 351. PHYSALIA ARETHUSA Til. (L. Agassiz.) 214 



352. Bunch of single Hydras and clusters of Medusas of Physalia. (L. Agassiz.) . 215 



353. Bunch of Hydras. (L. Agassiz.) 215 



" 354. Bunch of Medusas in various stages of development. (L. Agassiz.) . . 215 



" 355. Enlarged view of one of the fertile Hydras of VELELLA MUTICA. (L. Agassiz.) 216 



" 356. Velella, seen from below, to show the Hydras. (L. Agassiz.) . . . . 216 



" 357. Magnified view of a free Medusa of Velella mutica. (L. Agassiz.) . . . 216 



" 358. Magnified view of extended Hydroids of MILLEPORA ALCICORNIS. (L. Agassiz.) 219 



" 359. Branch of Millepora alcicornis, natural size. (L. Agassiz.) . . . . .219 



360. Transverse section of a branch. (L. Agassiz.) 219 



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