52 



the species can therefore verj' easily spread; but as it is a faet that they do 

 not do so, we must look for special catises that limit their distribution, regulate 

 it, and arrauge the animals as they have evidently been arranged from times 

 immemorial — It is often said that the animals are to be fouud where 

 their food is. But as the food consists in other animals or piants, or in parts 

 of such, the occurreuce of the food, sure enough, maj?- furnish an explanation 

 with respect to cerlaiu animals; but then we stop again by the question: what 

 then regulates the distribution of the food-auimals (piants)? It is cousequently 

 a provisional solution ouly, this reference to the food. The distribution of the 

 food is scarcely of any great importance to the animals on the bottom of the 

 Skager Rack; for it is evidently the mud of the liottom which affords the 

 means of subsistence to most of the invertebrates, and the rest of the animals 

 live on this invertebrate-fauna. The nourishing iugredients of the bottom- 

 materials, certainly, might occur in different quantities on the various depths 

 — it would be of interest to get this investigated — but however the distri- 

 bution might prove to be, it will never be able to explain, why some species 

 live on great depths only and not on less deep water, while others do just the 

 contrary. 



Besides time and space, and the ocrurrence of the food, there is still an- 

 other conditiou, which is often said to be of great moment when we want 

 to understand tlie distribution of the organisms, i. e. the conipetition hetween the 

 species, partly between those which are nearly allied to one another, partly 

 between the species less nearly related. And, certainly, there eau be no doubt 

 that in mauy cases the mutual relation between the various species has a great 

 influence on their distribution; many parasites are bound to a certain host and, 

 cousequently, can occur ouly witbin the province of distribution of the said 

 host. Certain animals may pursue others, which they want for their food, or 

 with which they compete in other ways, so vehemently tliat they drive them 

 away from districts, where they would otherwise have been able to live. But 

 I can scarcely believe that this circumstance is of any moment to the greater 

 part of the inhabitants of the sea. At any rate we must not forget that there 

 are many other factors which influence the distribution. Among these Fshall 

 mention the lii/ht in fhe various depths, the temperature, the salinity, the gas- 

 contents of the water (carbonic acid and oxygen), the specific gravity of the tvater, 

 the pressure, etc. 



There can be no doubt that the chauging light must have a powerful 

 influence on the distribution of the organisms (animals as well as piants), on 

 a slope extendiug from the shores as far as out on 300 fathoms' depth. Many 



