566 



DEPTHS OF THE OCEAN 



Fig. 392. 

 A ulographis pandora, Haeckel (about '/') 



(From Haecker. ) 



distribution of these forms, and found the small one (var. typica) occur- 

 ring in all depths, the large one (var. bathybia) in depths between 400 



and 1000 metres ; 

 ^ .J. the giant form 



V , occurs very rarely 



i n N o r w e g i a n 

 fjords. 



The Challenger- 

 idae have an q%^ or 

 lentil-shaped silici- 

 ous shell of most 

 delicate structure, 

 the aperture being 

 provided with a 

 collar or tube- 

 shaped moulding 

 (see Fig. 394). 

 They occur in all 

 oceans, but some- 

 times their distribu- 

 tion is very peculiar, 

 for some species live 

 only in abyssal 

 depths under the 

 equator, others at 

 both poles, others only in Antarctic waters ; some species live in the sur- 

 face waters, others between 50 and 400 metres, others between 400 and 

 1000 metres, others again 

 between 1500 and 5000 

 metres. From Haecker's 

 report on the Radiolaria 

 of the " Valdivia " Expedi- 

 tion we reproduce some of 

 these species. Protocystis 

 {Challengeri a) tridens 

 (Figs. 394, 2 and 3) occurs 

 in the northern and south- 

 ern cold zones, having 

 been taken as far north 

 as Spitsbergen, in the 

 Norwegian fjords, the 

 Skagerrack, round Green- 

 land, in the Labrador cur- 

 rent, and also in Antarctic 

 waters by the " Valdivia " ; 

 in Norwegian waters it has 

 been taken in deep water 



up to 50 metres below the surface. P. swirei (Fig. 394, 1) has been 

 taken only in the Antarctic from the surface down to a depth of 4000 

 and 5000 metres. P. tJwmsoni (Fig. 394, 4) belongs to a group of 



Fig. 393. 



Aulacantha scolymantha, Haeckel. a, var. typica ; b, var. 



bathybia, deep-sea form. (After Haecker, from Steuer. ) 



