178 J. W. Fewkes — Deep-Sea Medtisce. 



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 col- 

 lecting of deep-sea animals, observe with care the contents of 

 the dredges for attached Scyphostoma and Lucernarians, and 

 it is particularly desirable, from a morphological standpoint, 

 that the development of such genera as Atolla be known. 

 If it can be shown that this and related medusae have an indi- 

 rect development, with an attached Strobila living in great 

 depths, they may rightly be called deep-sea medusae. A nom- 

 adic jelly-fish, limited in bathymetrical habitat, could best ful- 

 fill its conditions of life by having a direct development with- 

 out attached larval conditions. 



Why cannot we suppose that deep-sea medusae 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 fins, of water, and 

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

 can endure these widely different conditions, they do not re- 

 semble 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 the littoral zone, would seem to be 

 true of animals which are not fixed to the ground nor depend- 

 ent upon it, viz : that there are bathymetric limits in the ocean, 

 even to nomadic animals apparently as helpless as the medusae. 



In closing my short discussion of the question of deep-sea 

 nomadic medusan life, it can be said that as far as the data 

 thus far gathered goes, neither the recorded depths, nor the 

 structure of the genera considered, demonstrates that we have 

 a serial distribution of free medusae in bathymetrical zones. 

 While our present information is insufficient to answer the 

 question, it seems to me that the case is much stronger than 

 the arguments which can be advanced in its support. There 

 is little doubt that medusan life has bathymetrical limita- 

 tions. Our well-known surface medusae probably cannot live' 

 at great depths, and their places are probably taken there by 

 others ; still, until there are more exact data bearing on this 

 conclusion, it cannot be demonstrated to be true. What is 

 now needed is, in the first place, an accurate determination 

 of the depth at Avhich medusae of different genera are captured, 

 and secondly a more accurate study of peculiarities of anatomy 

 and development of those which are supposed to be thus lim- 



