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 bathypelagie investiga- 
tions under the four following heads: 
(1) The portion of the Mediterranean investigated showed a rich pelagie fauna at 
the surface as well as at all depths up to 1,400 meters. 
(2) Pelagic animals which during the winter and spring appear at the surface seek 
deep water at the beginning of summer. 
(3) At greater depths occur pelagic animals which have hitherto been seldom or 
never observed at the surface. 
(4) A number of pelagic animals also remain at the surface during the 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 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 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” (15, p. 49). In consequence of his obser- 
vations on the periodic rising and sinking of pelagic animals, Chun 
‘ean not resist the impression 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, 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 animal 
groups can endure the high temperature of the surface water during 
the summer; the majority withdraw from the influence of this by 
sinking, and, finally, whole groups pass their life in the cool dem | 
regions aire 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 Atlanti¢ | 
Ocean ona trip made in the winter of 1887-88 to the Canary Islands 
(16, 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 water), 
and that among other things the occurrence of the full moon exerted 
a significant action (16, 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 
