570 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



depths, and completely overthrew the assumption that an azoic layer 

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

 embraced the general results of his important bathyi^elagic investiga- 

 tions under the four following- heads: 



(1) The portiou of the Mecliterrauean iuvestigated showed a ric-li pclanio fauna at 

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



(2) Pelagic animals which during the winter and spring a])pear at the surface seek 

 deep water at the beginning of summer. 



(3) At greater depths occur pelagic animals whicli have hitherto beeu seldom or 

 never observed at the surface. 



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

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



Among the remarks which Chun made on the vertical distribution of 

 the pelagic fauna and the astonishing plaiiktouic 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 tlie surface as well as to the sea bottom! 

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

 to the changing conditions of existence at the surface that they no 

 more seek the deeper levels " {1.% p. 40). In consequence of his obser- 

 vations on the periodic rising and sinking of pelagic animals, Chun 

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

 in the de])ths the surface fauna represents relatively only an advance 

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

 less extent, and occasionally completely, withdraws 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 auimal 

 groups can endure the high temperature of the surface water during 

 the summer; the majority withdraw from the influence of tliis by 

 sinking, and, finally, whole groups pass their life in the cool deep 

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



The general ideas which Chun had 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 1887-88 to the Canary Islands 

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

 wandering of pelagic animals in a vertical direction was influenced in 

 great part by ocean currents (at the surface as well as in deep wafer), 

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

 a significant action (10, p. 32). Chun's special observation 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 



