170 J. W. Feivkes — Deep-Sea Medusae. 



brought on deck. " In most cases," writes Prof. Verrill, " it is 

 impossible to say whether the novel forms of medusse taken in 

 the trawl and trawl wings are inhabitants of the bottom waters 

 or the surface, or of intermediate depths. Eventually those 

 that belong to the surface fauna will doubtless be taken in the 

 surface-nets, but this will require much more extensive collect- 

 ing of the surface animals than has yet been attempted." 



It will thus be seen that the means of determining the depth 

 at which the collecting of free oceanic animals takes place are 

 too imperfect for any accurate knowledge of the bathymet- 

 rical limits of so-called deep-sea medusae We are in fact on 

 the very threshold of this kind of research, and what is now 

 most needed, in the study of bathymetrical zones of marine 

 life, are improvements in methods of collecting at any depth, 

 so that we can tell exactly at what distance below the surface 

 a nomadic animal is captured. Devices have been suggested, 

 one of which, the so-called " Gravitating TrajD," of Lieut. 

 Sigsbee, has been described in the Bulletin of the Museum of 

 Comparative Zoology at Cambridge. I am not aware how ex- 

 tensively this apparatus, or others of similar kind, have been used 

 by those who are in charge of deep-sea exploration, or whether 

 it has been sufficiently tried to test its usefulness * If medusae 

 were always as abundant at great depths as they sometimes are 

 at the surface, a device might easily be invented for the suc- 

 cessful capture of at least a few specimens. It seems more 

 probable that medusae are not common enough to warrant 

 one in supposing them very numerous, and the difficulty in 

 their capture thus becomes greater, rendering it necessary that 

 some modification of the gravitating trap be invented.f 



In a letter to Mr. C. P. Patterson (Bull. Mus. Comp. Zool., 

 vol. vi, ~No. 8) Mr. A. Agassiz calls attention to the uncertain 

 methods adopted for ascertaining at what depths free-swim- 

 ming animals live, and from experiments with the " Sigsbee 

 Trap " concludes (p. 153), while he does not deny that there 

 are certain genera of deep-sea medusae, that " The above experi- 

 ments appear to prove conclusively that the surface fauna of 

 the sea is really limited to a comparatively narrow belt in depth, 

 and that there is no intermediate belt, so to speak, of animal 



* Results of Explorations made by the Steamer Albatross off the Northern 

 coast of the United States in 1883. Annual Report Com. Fish and Fisheries, 1883. 



f The small amount of water wbich enters the Sigsbee gravitating trap is one 

 great objection to it. Negative results with this apparatus do not necessarily 

 show that life does not exist at the depth at which the door is opened, and the 

 instrument does not collect from a large enough area for a successful determina- 

 tion of the abundance of life which it is intended to capture. From what has 

 been published, and statements of those engaged in deep-sea exploration, I am 

 led to suppose that the "Sigsbee Gravitating Trap " has given only negative data 

 in regard to the problem of the existence of characteristic nomadic life in inter- 

 mediate depths of the sea. 



