Remarks on Myctophum glaciale (Reinh.). 19 
inference. Apart from the eggs and the young stages and some 
slow-swimming species all which may be classed among the 
the plankton, I do not think pelagic fishes in general are directly 
influenced much by the movements of the water-layers. 
The currents of the oceans have been — and still are — 
natural highways of distribution for the marine organisms in like 
manner as the large valleys are for the animals of the dry land. 
In both we find the conditions of life characteristic of the starting- 
region continued in a certain direction and gradually altering 
into those of another faunal area. How far each species will 
gain ground is finaliy contingent upon its claim on life — its 
biological character. 
The Gulf Stream represents a continuation of the Atlantic 
conditions of life (temperature, salinity) into the boreal region; 
the northern limit of distribution of the Atlantic forms thus 
becomes more or less vague in this direction. When especially 
those pelagic fishes, which have been found stranded along our 
coast or floating at the surface, are considered, these finds (together 
with an unconscious influence of the word “current”? on ones 
reasoning) may lead to the idea that the Atlantic forms of the 
Norwegian Sea are the dying remnants of the fish-community 
of southern latitudes which the current has carried northwards. 
That the selection of species represented in northern waters is 
mainly due to differences of the species in biological respect 
rather than to a varying degree of power of resistance to the 
mechanical force of the current will, I think, become evident 
when not only those species, which are known from northern 
waters, are taken into consideration, but also those that are 
wanting. Eggs and larve are drifting with the current but as 
these stages are most sensitive to variations of the medium it will 
also here be the biological causes that decide whether the trans- 
port shall produce a result or not. 
The Atlantic representatives among the fish of the Norwegian 
Sea and the Norwegian coast are mainly found among the plankton 
feeders and the roaming rapacious fishes. In case the mecha- 
nical effect of the current was the decisive point with regard to 
the occurrence of the Atlantic species in the Norwegian Sea, it 
might have been expected that the transport took place the year 
round, but the principal spurt seems to be made in spring when 
