Mr. J. W. Fewkes on Deep-sea Medusae. 259 



the only genera in the above list which can be regarded as 

 purely deep-sea in their habit. Each of these is described 

 from single specimens, and the former is closely allied to well- 

 known surface-genera. The foundation in observation for a 

 belief in the existence of nomadic deep-sea Medusse, as far as 

 recorded depths go, is certainly not all that might be desired. 



Possibly a stronger argument for the existence of deep- 

 sea Acraspeda may be drawn from the structure of the 

 interesting free genus of Lucernarid^ {Lucernaria hathyphila, 

 Hseck.). This species is recorded from 540 fath. The fixed 

 Lucernarice are found in shallow water. The argument 

 drawn from the structure of the free Lucernarian would be 

 stronger if the so-called attached species had been brought up 

 from great depths or if Scyphostoma had been reported from 

 the ocean bed. It is suggested that those who have in 

 charge the collecting of deep-sea animals observe with care 

 the contents of the dredges for attached Scyphostoma and 

 Lucernarians, and it is particularly desirable, from a morpho- 

 logical standpoint, that the development of such genera as 

 AtoUa be known. If it can be sliown that this and related 

 Medusae have an indirect development, with an attached 

 Strobila living in great depths, they may rightly be called 

 deep-sea Medusge. A nomadic jelly-fish, limited in bathy- 

 metrical habitat, could best fulfil its conditions of life by 

 having a direct development without attached larval con- 

 ditions. 



Why cannot we suppose that deep-sea Medusse can live at 

 the surface and also at great depths ? Why look for bathy- 

 metrical zones in the ocean for nomadic animals ? The main 

 reason seems to be the exceptional nature of such a wide dis- 

 tribution in places so widely separated in physical character- 

 istics. It may be possible for a Medusa to live equally well 

 at the surface and under a pressure of 2000 fath. of water, and 

 in the different temperatures of these two regions ; but if they 

 can endure these widely different conditions, they do not 

 resemble other animals and their own relatives from the 

 shallow waters. The logical inference from what is known 

 of the differences between the facies of deep-sea animals on 

 the ocean-bottom and those from tlie littoral zone would seem 

 to be true of animals which are not fixed to the ground nor 



Thomas Lee, who has seen the genua when collected, informed me, after 

 I had shown him a specimen of AtoUa, that he remembers it in deep- 

 water trawls. In new collections made by the ' Albatross ' in 1885-86, 

 Atolla in several instances is recorded from the " surface," and one of 

 those described iu the collections of 1888-84 is recorded from the surface. 



