PELAGIC ANIMAL LIFE 619 



In describing the pelagic communities of the open Atlantic 

 it is therefore natural to treat each of these three regions 

 separately, and to consider the pelagic communities of the coast 

 banks as a fourth biological region. 



Bathypelagic Comuiiinities in Depths greater than §00 

 Metises. — The most abundant fishes in this region are two 

 Sternoptychidse of the genus Cyclothone, viz. C. signata and 

 C. luicrodon. 



Of these two species we caught altogether over 7500 Vertical 

 individuals, which were all measured and arranged according cj^/w! 

 to their length and the instrument in which they were captured, 

 so as to obtain information regarding the occurrence of the 

 different sizes at different depths. Fig. 473 shows, in the 

 case of both' species, the results of the catches made between 

 Newfoundland and Ireland. 



Cyclothone niicrodon was found during the cruise of the 

 " Michael Sars " in the North Atlantic at every station where 

 an appliance was towed in depths below 500 metres. Above 

 500 metres it was met with only occasionally, and at a depth of 

 300 metres we came across only one individual. In depths 

 from 500 metres down to 1500 metres its quantitative occurrence 

 appears to be fairly uniform. 



In our northern as well as in our southern section we found 

 approximately the same number of individuals in each of 

 the three young- fish trawls which we towed simultaneously 

 at depths of 500 metres, 1000 metres, and 1500 metres. At 

 depths below 1500 metres we made only a few hauls, though, 

 on the other hand, we carried out some vertical hauls, which 

 allow of a comparison between the quantity met with above 

 and below 1500 metres. At Station 63 (in the northernmost 

 portion of the Sargasso Sea) we secured ten individuals in a 

 haul from a depth of 4500 metres up to 1500 metres, and 

 twenty-seven individuals in a haul from 1350 metres up to 450 

 metres. Accordingly, seeing that the first haul was made 

 through a distance more than three times as great as the 

 second, we get the result that there were nine times more 

 individuals in the intermediate layer from 1350 metres up to 

 450 metres than below 1500 metres. A more complete 

 analysis of the different depths from 1500 metres down to the 

 bottom of the sea (about 5000 metres) would have been very 

 desirable, but unfortunately we were unable to spare time for 

 it. It may be that there is a layer at the lowest depths where 

 there are no individuals, and I, for my part at any rate, cannot 



