254 Mr. J. W. Fewkes 07i Deep-sea Medusae. 



light never penetrates. We may have here what we so often 

 find in deep-sea animals, a reduction in the size and efficiency 

 of the special organ of sense to fit the Medusa for the condi- 

 tions under which it must live at great depths. Stated in a 

 startling way, we might speak of Atolla as a blind Medusa. 

 This statement would hardly be justifiable, and we can at 

 present go no further than to say that the special sense-bodies 

 of sight * are supposed to be rudimentary. It must, how- 

 ever, be borne in mind that nowhere among Acraspeda do we 

 have so many, twenty-two, sense-bodies as here. In some 

 specimens there are twenty-eight sense-bodies in this genus. 



It is extraordinary that one of the known species of Atolla 

 [A. Wyvillii^ Haick.) comes from the Antarctic Ocean, while 

 our two species were both from the warm (?) water of the 

 Gulf-stream. In the southern hemisphere its lowest limit 

 is about 2000 fathoms, while north of the equator it comes 

 from the surface or within a few hundred fathoms. 



Among the Medusas collected by Lieut. Greely in the icy 

 waters of Lady Franklin Bay is an interesting jelly-fish allied 

 to Atolla. This genus (Nauphanta) has been found but once 

 before, and then by the naturalists of the ' Challenger ' in the 

 neighbourhood of the island of Tristan d'Acunha in the South 

 Atlantic. In the latter locality it is recorded from about 1500 

 fathoms, while in Lady Franklin Bay it is found at the sur- 

 face. From several differences in these two specimens, those 

 from the Arctic and those from the South Atlantic, I have 

 supposed the boreal form to be new and have called it by the 

 specific name polaris f. The ' Challenger ' s])eciraens were 

 placed under a new genus, called by Hajckel Nauphanta \. 



Before we consider the relationship between Atolla, Nau- 

 phanta, and other related Medusas ascribed to the deep sea, 



* Whether the " eye " of the jr'lly-fish can distinguish form or not has 

 not been demonstrated. Simple experiments made by passing rays of 

 light through dishes in which they are confined, or the simple fact that 

 they almost always congregate on the illuminated side of the same, are 

 not conclusive to me that they distinguish /iyrwt. Experiments with sen- 

 sitive plates to show the depths to which light penetrates the water are 

 most suggestive in this connexion. It seems pertinent to the whole 

 inquiiy to ask whether looked at from the physical side there are not rays 

 of light of such a nature that the vertebrate eye is not able to perceive 

 them, but which may act upon the visual organs of other animals. 



t Nauphanta polaris has a central disk as in Atolla, a coronal fossa, 

 and a corona, which, however, is formed of sixteen socles, eight of which 

 bear tentacles, tentacular socles, and eiglit sense-bodies. The outlines of 

 these socles is more clearly marked than in Atolla on the upper surface of 

 the corona which they form, on account of the deep sculpture which 

 separates them. 



\ The name NaujiJuatta was preoccupied in 1879, when applied to this 

 Medusa, having been given to a worm in 1864, 



