596 REPORT OF COMMISSIONER OF FISK AND FISHERIES. 



amongj tbe Acraspedota. Some Meduscc have j^artly or entirely given 

 up tbe swimming- mode of life, as Polyclonia^ Cephea, aud other Rhiz- 

 osfo))ia, which lie with the back towards the sea bottom, the iiiany- 

 mouthed bunch of tentacles directed upwards. The Lucernaridw have 

 completely passed over to the benthos. Mnny.l/ert^sft' are spauipelagic, 

 rise to the surface only during a few mouths (for the purpose of reproduc- 

 tion!), and pass the greater part of the year in the depths; thus in the 

 Mediterranean the beautiful Cotylorrhiza tuberenlata, Chdryhdea marsu- 

 pialis, Timajfavilabris, and OUndias miilleri. These bathybic forms are 

 sometimes brought up in great numbers with the bottom net (19, p. 122). 

 Many cling with their tentacles to Alr/fc and other objects (20, p. 341). 



The immense swarms in which the MednMv sometimes appear, millions 

 crowded thickly together, are known to all seafaring naturalists. 

 Tlius in Arctic waters, Codon'mm princcp^^^ Hippocrene superciliaris; in 

 tlie North Sea, Tiara pilcata, Aglantha digitalis; in the Mediterraiieau, 

 Liriantha mncronata, Rliopalonema velatum; in the tro^ncs, Cytms 

 nigritina; in the Antarctic Ocean, Ilippocrene mocloriana and others. 

 Hensen (9, p. 05) in the North Sea found a swarm of Aglantha^ the 

 number of which he estimated at twenty-three and one-half billions. 

 The extent of the multitude was so great that "the thought of approxi- 

 mately estimating the animals in this swarm must be given r.p." In 

 such cases the whole sea for a few days, or even weeks, seems every- 

 where full of Mediisw; and then again weeks, or even months, may jiass 

 without finding an individual. The uncertainty of appearance, the 

 " capriciousness of these brilliant beauties," in other words the depend- 

 ence upon many different, ancl for the most part unknown causes, is in 

 this interesting animal group remarkably impressed upon us. I will, 

 therefore, in another place, referto it orithe ground of my own experience. 



Siphonophorcs. — What I have said above concerning the unequal dis- 

 tribution of the medusa? applies also to their wonderful descendants, 

 the purely oceanic class of the siphonophores. This highly interest- 

 ing class was, up to a few years ago, also regarded as purely jjelagic; 

 but of these, too, it is now known that they are in great part bathy- 

 pelagic, in part also zonary and bathybic. The new and very peculiar 

 groui^ of the Ai(ronecfa' {Steplialida' and BJuMlalida'), taken by the Chal- 

 lenger at a depth of 200 to 000 fathoms, is described in my '^ Report of 

 the Siphonophores of H. M. S. CMllenger'^ (1888, p. 290). The Batky- 

 phy.sa taken by Studer, and some of the Rliizopliysidw [Auropkysa^ Lino- 

 pliy^a) captured by the Gazelle, were taken at a dej)th of 000 to 1,000 

 fathoms (1. c). But that such deep-sea siphonophores (probably mostly 

 RhizopJiysida') inhabited the ocean in great masses was first shown by 

 Chierchia (8, p. 84-80). Previously, in numerous soundings which the 

 Vettor Pisani had made in the Atlantic and Pacific oceans, the line of 

 the deep-sea lead when drawn up was found to be wound around with 

 the torn-off stinging tentacles of great sij)honophores. By means of 



