xiv LIST OF THE WOOD-CUTS. 



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



320. Profile of Ectopleura ociiracea, magnified 191 



321. The .same, seen from the abaetinal pole . . . . . . . .192 



322. The same, seen from the attinal pole ........ 192 



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



324. Medusa of CouYMORPiiA I'ENDULA, seen in profile. (H. J. Clark.) . . 193 



325. Single Hydra of Hybocodon prolifek. (L. Agassiz.) 193 



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



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



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



329. Part of male community of IlYDRACTi.vtA POLYCLIN.4. (L. Agassiz.) . .198 



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



331. Oil-float of Nanomia caka, magnified 200 



332. Nanomia cara, natural size 201 



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

 tubes 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 Medusa; (Polyps) of first kind formed, with knob-shaped tentacles . 204 



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



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



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



342. Cluster of Medusa; (Polyps), in difi'erent stages of development, before the ap- 

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



343. Knobs like those of Fig. 339, in <iifterent 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. PirYS.iLi.*. Arethusa Til. (L. Agassiz.) 214 



352. Bunch of single Hydrae and clusters of Medusae of Physalia. (L. Agassiz.) . 215 



353. Bunch of Hydra;. (L. Agassiz.) 215 



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



355. Enlarged view of one of the fertile Hydra- of Yelella mutica. (L. Agassiz.) 216 



356. Yelella, seen from below, to sliow the Hydra;. (L. Agassiz.) .... 216 



357. Magnified view of a free Medusa of Yelella mutiea. (L. Agassiz.) . . . 216 



358. Magnified view of extended Hydroids of Mn.LEPORA alcicornis. (L. Agassiz.) 219 



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



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



