io6 DISCOVERY REPORTS 



Table 4. The bathypelagic species of Leptolina behave in the same manner as the bathypelagic 

 Trachyhna. The majority of the bathypelagic species are almost cosmopolitan in the deep parts of 

 the oceans, and several species occur in the 'warm deep water' of the antarctic region; but some 

 species require a slightly higher temperature. Ekman (1953, p. 365) calls attention to the interesting 

 fact that 'the comparatively slight difference in temperature between 3° and 0° or i*^ seems in this 

 case to be decisive '. This evidently applies to these few species of bathypelagic medusae, whereas a 

 greater number of species may endure the lower temperatures in the deep water below the antarctic 

 surface water. 



The distribution of medusae, as of other pelagic animals, affords a multitude of highly interesting 

 problems, and only some few of them are touched upon in the present paper. There are still extensive 

 areas of the sea which are insufficiently investigated, but the comprehensive collections of the Dis- 

 covery Investigations have contributed greatly towards a better understanding of many problems, 

 the more so because the great majority of the specimens are well preserved. Certain determination 

 of the species was therefore possible, and it should always be borne in mind that this is a necessary 

 condition to every discussion of distributional questions. 



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