GENERAL BIOLOGY 699 



gravity and viscosity as in the Norwegian Sea, and also the 

 same temperatures. These Boreal species are essentially larger 

 than the warm-water forms belonging to the Atlantic surface- 

 layers, and have far smaller organs of floating. This applies 

 equally to the genuine deep-sea forms of the Atlantic in whose 

 company the boreal forms are found (see, for instance, what I 

 have previously said about the radiolarians, the trachymedusse, 

 and the crustaceans). A parallel is also found in fishes and 

 squids, of which some larger forms commence to appear in the 

 deeper layers, their size apparently increasing as we descend 

 towards the bottom (compare the measurements of Cyclothone 

 signata and C. micj^odon, Fig. 473, p. 620, and the two figures 

 representing ripe Cyclothone, Figs. 527 and 528). The bathy- 

 pelagic Gastrostomus dairdii, one of our deepest-living pelagic 

 fishes, was found to attain a length, including its long tail, 

 of 75 cm. In these regions we also find large prawns, which 

 appear to increase in size with increase of depth [Acantkepkyra, 

 Notostomiis). The squids seem to be arranged in two 

 groups, a number of small forms living in the upper layers 

 and the larger species living in deeper water. Although our 

 captures from a systematic point of view may be characterised 

 as exceedingly rich, they are not satisfactory for a study of the 

 vertical size-distribution of squids. 



The peculiar agreement between size, form, and distribu- coast waters. 

 tion of species and the occurrence of a certain specific gravity 

 and viscosity of the water seems entirely absent in coast waters, 

 where the specific gravity of the water is lower than in the ocean, 

 because the inflow of fresh water from continental rivers lowers 

 the salinity. The viscosity, mainly dependent on temperature, 

 should, as a rule, be similar to that of the open ocean outside. 

 One would therefore expect to find, for instance on the coast 

 banks of Africa, similar oceanic forms, or the same faunistic 

 characters on the whole, as in the Atlantic Ocean, On the 

 contrary, we find that the fauna as well as the flora have 

 entirely different features. For unicellular plants as well as for 

 animals, the rule holds good that all forms are much larger 

 than those in the open ocean. Among plants the minute cocco- 

 lithophoridae are replaced by peridineae ; instead of the minute 

 oceanic scopelidse we meet with pelagic herrings and mackerels, 

 animals of quite another size and character. 



As to the northern part of the Atlantic we perceive that 

 several boreal forms (among others Clione Ih?iacina), which in 



