928 REPORT OF COMMISSIONER OF FlSH AND FISHERIES. [2] 



tbe pelagic life claimed to have been taken at diflerent depths, we are 

 hardly able to definitely state the peculiar characteristics or limits of 

 different bathymetrical zones, as far as those animals which do not live 

 on the bottom are concerned. 



There is no other group of marine animals better suited than the me- 

 dusfe to test the question of whether free-swimming marine animals are 

 represented at great depths by peculiar genera or not, and even before 

 direct observations bearing on this point were made it was pretty gen- 

 erally believed that a knowledge of these animals, if such there be, was 

 destined to throw some light on questions of the bathymetrical distri- 

 bution of pelagic animals. If the recorded depths from which medusie 

 are found can be trusted, the results of the voyage of the Challenger, 

 bearing on this point, show that the medusan group has a great bathy- 

 metrical distribution. From new facts published in the present paper 

 1 am not sure that we can suppose certain of the medusai recorded by 

 the Challenger from great depths do not also live and flourish at or 

 near the surface. It is not in the province of this paper to examine.the 

 methods by which it is known that a genus recorded from, for instance, 

 1,200 fathoms really came from that depth. I leave this question to the 

 collector; but it may be well to remind the reader that the methods of 

 determining the exact depth at which a free-swimming animal entered 

 the dredge, or in case of a RMzophysa, became entangled on the rope, 

 may or may not be the depth of the sounding. There is a call for greater 

 accuracy in a determination of the exact depth from which a deep-sea 

 medusa is taken, and for an improvement of apparatus used in this 

 kind of collecting. In the case of fixed hydroids, or such meduste as 

 Cas.siopea and others, which live ui)on the bottom, the determination of 

 the depth at which they live is an easy task. With genera as Atolla, 

 Bhizophysa, and others, this determination is more difficult. The depths 

 at which medusoe are reported in the present paper, and the same is 

 probablj* true of those recorded by Ha^ckel, Studer, and others, must 

 therefore be viewed in the light of what has been said above. There is 

 no reason to deny the existence of deep-sea medusa? confined to great 

 depths, and on the other hand nothing to show, without doubt, that the 

 same jelly-fishes, with the exception of those mentioned, are not also 

 found at the surface.* 



The importance, from a morphological standpoint, of definitely an- 

 swering the question whether medusse are confined to certain depths is 



* We can hardly hope, in the imperfection of our knowledge of the limits of the hab- 

 itat of the so-called deep-sea medusEe, for an answer to the many interesting ques- 

 tions concerning them which are suggested hy this condition of life. Of the nine 

 Craspedote medusBB which, according to Hajckel, "have either adapted themselves 

 by special modilicatious of organization to such a mode of life, or which give evidence 

 by their primitive structure of a remote phylogenetic origin," one genus at least is 

 known to come to the surface. Atolla, which is certainly one of the most striking of 

 these genera, was takea in one instance {A. Bairdii) from the surface waters of th^. 

 Gulf Stream, 



