ANIMAL LIFE IN THE SEA 177 



(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 fioating wreckage, 

 with a burden of attached invertebrates, such as 

 Crustacea, &c., drew them to the surface. Among the 

 surface forms may be noted the fi3dng-fish (Eiocoetus), 

 the beautiful ' dolphin ' (Coryphaena), and its alhes, 

 the bonito (Thynnus pelamys), another fiying form, 

 related to the mackerel, which is also pelagic. All these 

 forms, however, despite their obvious adaptations to 

 pelagic fife, are more abundant as the land is approached 

 than far away from land. 



The abovei 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 ocpur 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 compKcated 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 



1404 M 



