xiv LIST OF THE WOOD-CUTS. 



One of the tentacles, seen in profile 190 



Profile of EcTOPLEURA OCHRACEA, magnified 191 



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



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



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



iledusa of Corymorpha pexdula, seen in profile. (11. J. Clark.) . . 193 



Single Hydra of Hybocodon prolifer. (L. Agassiz.) 193 



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

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



Medusa bud of Hybocodon prolifer. (L. Agassiz.) 194 



Part of male community of Hydractixia POLYCLiNA. (L. Agassiz.) . .198 



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



Oil-float of Naxomia cara, magnified 200 



Nanomia cara, natural size .......... 201 



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



tubes 202 



The same bell, from the actinal pole 202 



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



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



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



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



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



Second kind of Medusae, with cork-shaped tentacles ...... 205 



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



Cluster of Medusae (Polyps), in different stages of development, before the ap- 

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



Knobs like those of Fig. 339, in diff'erent stages of development . . . 207 



Same kind of knob, still further developed 207 



Young scale, seen from different sides 207 



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



Somewhat more advanced .......... 208 



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



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



Still more advanced Nanomia .......... 209 



Young Nanomia, where we find several Medusae of the first kind . . . 209 



Physalia Arethusa Til. (L. Agassiz.) 214 



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



Bunch of Hydrae. (L. Agassiz.) . . .215 



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



Enlarged view of one of the fertile Hydrae of Velella mutica. (L. Agassiz.) 216 



Velella, seen from below, to show the Hydrae. (L. Agassiz.) . . . . 216 



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



Magnified view of extended Hydroids of Millepora alcicorkis. (L. Agassiz.) 219 



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



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



