66 BRUUN 



In 1943 Spirula was shown as having a world-wide distribution in 

 tropical and subtropical regions, being most common near the steep 

 slopes of continental and island shelves. The vertical distribution was 

 given as 200-1750 meters, except in areas of upwelling, where the animal 

 is found at 100 meters. Thus it would belong neither to the surface 

 group nor to the true bathypelagic species. It was also stated that its 

 distribution, considered as a whole, was not clearly limited by any single 

 factor. It is the lower depth limit which should be studied further because 

 it was based on a statistical treatment of catches from open nets. The 

 upper hmit, however, was quite well fixed because a large number of 

 negative hauls had been made between it and the surface in areas where 

 Spirula is caught regularly in deeper layers. The important factor in the 

 depth range is the temperature. 



Observations made by the Dana in 1930 indicate the temperature 

 conditions in the Mozambique Channel close to Galathea Station 203. 



Depths in meters Temperatures, Centigrade 



Dana Station 3962 Dana Station 3964 



24°33' S., 38°26' E. 25°14' S., 36°2l' E. 



26.50 28.56 



100 23.03 24.56 



200 19.73 20.67 



300 15.46 16.76 



400 13.84 14.42 



500 12.56 12.84 



600 11.38 11.38 



800 9.60 9.10 



1000 7.23 7.10 



At Galathea Station 203 the catch must have been made between 

 the bottom (greatest depth, 720 meters) and about 200 meters; hence 

 the temperature range must be between 10° and 20° C. The lower limit 

 (10° C.) is just about the temperature which can be used for practical 

 purposes to distinguish between the upper warm water masses, the ther- 

 mosphere, and the deeper cold water masses, the psychrosphere, of the 

 lower ocean latitudes. The polar limits of the thermosphere occur where 

 the 10° C. isotherm comes to the surface. 



