PELAGIC ANIMAL LIFE 



581 



in subtropical seas where the surface temperature is very high, and 

 Dahl mentions this latter form as living in deep water in the Sargasso 

 Sea. 



Numerous investigations on the Copepoda of the Norwegian Sea have 

 in recent years been made by the " Michael Sars," the material having 

 been worked up mainly by Damas, whose results will be mentioned in 

 the sequel. From the Atlantic cruise of 1910 the " Michael Sars" also 

 brought home a large collection of Copepoda captured both in horizontal 

 hauls and in closing nets, and this material is at present being described 

 by Nordgaard and Lysholm, but their results are not yet ready for dis- 

 cussion. G. O. Sars has, however, been good enough to determine the 

 Copepoda for me in a few selected samples, and these determinations 

 are so interesting that I give in the following table the number of 

 species found at various depths : — 



Number of Species of Crustaceans, chiefly Copepoda, taken in 

 Closing Nets at the Stations specified 



The most northerly station (113) is relatively poor in species, especi- 

 ally in the deep cold layers, the richest station being the most southerly 

 one (50), and remarkably enough the richest sample is the deepest one 

 in 500 to 1000 metres, which contained twice as many species as the 

 surface sample. 



The Ostracoda are considered by Haeckel to be the most important Ostracoda. 

 group of Crustacea next to the Copepoda, being represented by a great 

 number of species. The "Challenger" collected 221 species, of which 

 52 were taken in depths greater than 500 fathoms, 19 beyond 1500 

 fathoms, and 8 beyond 2000 fathoms. Many ostracoda possess the 

 power of emitting intense phosphorescent light, and Haeckel narrates how 

 on his voyages to Ceylon he saw the entire sea like a continuously 

 twinkling ocean of light as far as the eye could reach ; the microscope 

 proved most of these luminous animals to be ostracoda, with some 

 medusae, salpae, and worms. 



Some of the surface ostracoda are very widely distributed, like 

 ConcJicecia elegans, which occurs all the way from the Norwegian Sea 

 to the Antarctic. In northern waters we may find also C. borealis and 

 C. obUisata. In Antarctic waters we find C. antipoda, closely resembling 

 C. obtusata of the north. As abyssal forms we may note the large 

 individuals (attaining i cm. in length) of the genus Gigantocypris 

 (see Fig. 419), recorded by the " Valdivia " from the Indian Ocean 

 and from the Atlantic between lat. 14" N. and 42° S., previously 



