SCIENTIFIC ADVANTAGES OF AN ANTARCTIC EXPEDITION. 419' 



currents of surface water drifted to tlie uortli. This warm underlying 

 water is evidently a i)oteut factor in the melting and destruction of the 

 huge table-topped icebergs of the southern hemisphere. While these 

 views as to circulation of oceanic water appear to be well established, 

 still a fuller examination is most desirable at different seasons of the 

 year, with improved thermometers and sounding machines. Indeed, 

 all deep-sea apparatus has been so much improved as a result of the 

 Challenger explorations, that the labor of taking salinity and all other 

 oceanographical observations has been very much lessened. 



PELAGIC LIFE OF THE ANTARCTIC OCEAN. 



In the surface waters of the Antarctic there is a great abundance of 

 diatoms and other marine alga;. These floating banks or meadows form 

 primarily not only the food of pelagic animals, but also the food of the 

 abundant deep-sea life which covers the floor of the ocean in these 

 south ijolar regions. Pelagic animals, such as copepods, amphipods, 

 mollusks, and other marine creatures, are also very abundant, although 

 species are fewer than in tropical waters. Some of these animals seem 

 to be nearly, if not quite, identical with those found in high northern 

 , latitudes, and they have not been met with in the intervening tropical 

 zones. The numerous species of shelled Pteropods, Foraminifera, 

 Coccoliths, and Ehabdoliths, which exist in the tropical surface waters, 

 gradually disappear as we approach the Antarctic circle, where the 

 shelled Pteropods are represented by a small Limacina, and the Fora- 

 minifera by only two species of Glohigerina, which are apparently 

 identical with those in the Arctic Ocean. A peculiarity of the tow-net 

 gatherings made by the Challenger^ expedition in high southern lati- 

 tudes, is the great rarity or absence of the pelagic larvte of benthonic 

 organisms, and in this respect they agree with similar collections from 

 the cold waters of the Arctic seas. The absence of these larvae from 

 polar waters may be accounted for by the mode of development of 

 benthonic animals to be referred to presently. It must be remembered 

 that many of these pelagic organisms pass most of their lives in water 

 of a temperature below 32° F., and it would be most interesting to 

 learn more about their reproduction and general life history. 



BENTHOS LIFE OF THE ANTARCTIC OCEAN. 



At present we have no information as to the shallow-water fauna of 

 the Antarctic Continent: but, judging from what we do know of the 

 ofl'-lying Antarctic Islands, there are relatively few species in the shal- 

 low waters in depths less than 25 fathoms. On the other hand, life in 

 the deeper waters appears to be exceptionally abundant. The total 

 number of species of Metazoa collected by the Challenger at Kerguelen 

 in depths less than 50 fathoms was about 130, and the number of addi- 

 tional species known from other sources from the shallow waters of the 

 same island is 112, making altogether 242 species, or 30 species less 



