570 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



depths, and completely overthrew the assumption that au azoic layer 

 of water exists between the surface and the sea bottom" (15, p, 2). Chun 

 embraced the jieneral results of his important bathypelagic investiga- 

 tions under the four following heads: 



(1) The portion of the Mediterrauean investigati'd sliowi'd a ricli ]><]a.ni<" fauna at 

 the surface as -well as at all dcptlis up to 1,400 meters. 



(2) Pelagic animals which during the winter and sj)ring ajijiear a1 tlic siii tact' seek 

 deep water at the beginning of summer. 



(3) At greater depths occur pelagic animals whitdi liavc Iiithcito Ihmii scldi-m <.i' 

 never observed at the surface. 



(4) A number of pelagic animals also remain at tlie surface during the summer, 

 and never sink into deep water (15, p. 44). 



Among- tlie remarks Avhich Chun made on the vertical distribution of 

 the pelagic fauna and the astonishing planktonic wealth of the depths 

 of the sea (at 1,000 to 2,000 meters), he Justly throws out the question, 

 "Who knows, whether in the course of time our views will not undergo 

 a complete reversal, and whether the depths^will not show themselves 

 as the peculiar mother earth of pelagic life, from which, for the time 

 being', swarms are sent out to the surface as well as to tlie sea bottom ! 

 There are only a few forms which can so completely adapt themselves 

 to the changing conditions of existence at the surfjice that they uo 

 more seek the deeper levels " (15, p. 40). In consequence of his obser- 

 vations on the periodic; rising and sinking of pelagic aninnils, Chun 

 "can not resist the imjiression that from the abundance of animal life 

 in the depths the surface fauna represents relatively only an advance 

 guard of the whole, which sometimes to a greater, sometimes to a 

 less extent, and occasionally completely, Avithdraws itself into more 

 protected regions. Facts plainly speak for this, that the periodical 

 wandering of pelagic animals in the vertical direction is especially 

 conditioned by the changes in temperature. Only a few pelagic animal 

 groups can endure the high temperatui-e of the surface water during 

 the summer; the majority withdraw from the intluenite of this by 

 sinking, and, finally, whole groups i)ass their life in the cool deep 

 regions without ever rising to the surface"' (15, p. 54). 



The general ideas which Chun bad obtained by this deep-sea inves- 

 tigation of the Mediterranean he was able to confirm for the Atlantic 

 Ocean on a trip made in the winter of 1887-S8 to the Canary Islands 

 (10, p. 31). At this time he made the observation that the periodical 

 wandering of jjclagic animals in a \'ertical direction was influenced in 

 great part by ocean currents (at the snrface as Avell as in deep Avater), 

 and that among other things the occurrence of the full moon exerted 

 a significant action (10, p. 32). Chun's special observati<m in the sea 

 of Orotava, upon the poverty of the Canary plankton in November and 

 December and the sudden appearance of great numbers and many 

 species of pelagic animals in January and February, agrees completely 

 with the observations which I myself made twenty years before at 



