ANIMAL LIFE IN THE SEA iy 
(Balaena, &c.) feed on the floating plankton, especially 
on sea-butterflies (Pteropods), and are very common 
in cool and cold waters, though widely distributed. On 
the other hand, the fish-eating dolphins and porpoises 
especially frequent shallow waters, where the fish on 
which they prey are most frequent. 
With the exceptions already given, purely pelagic 
fish are not very abundant, at least in the surface 
waters. The reason is apparently that food near the 
surface is not sufficiently abundant. Professor Bouvier 
notes that the Princesse Alice, the Prince of Monaco’s 
yacht, while cruising in mid-Atlantic, found practically 
no surface fish, except when some floating wreckage, 
with a burden of attached invertebrates, such as 
crustacea, &c., drew them to the surface. Among the 
surface forms may be noted the flying-fish (Exocoetus), 
the beautiful ‘ dolphin’ (Coryphaena), and its allies, 
the bonito (Thynnus pelamys), another flying form, 
related to the mackerel, which is also pelagic. All these 
forms, however, despite their obvious adaptations to 
pelagic life, are more abundant as the land is approached 
than far away from land. 
The above forms may be regarded as characteristic 
of the upper 100 fathoms or so of water. We have next 
to consider the mesoplankton and mesonekton—that is, 
the forms which occur between the surface layers of 
water and the bottom, near the light limit. The study 
of these is necessarily a difficult matter, involving 
the use of complicated methods not hitherto used at 
very great depths. Provisionally, however, the follow- 
ing statements may be made, these being based especi- 
ally on the results obtained by the Michael Sars 
expedition. 
At depths between 200 to 300 fathoms, but varying 
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