

'■'"'%. 



M^mK 



330 DEPTHS OF THE OCEAN 



Besides these highly-organised forms, which I have given 

 as instances, the peridineae include many with a far more simple 

 structure. There are, especially in the samples collected by 

 means of the centrifuge, numerous series 

 of small forms, both coloured and colour- 

 less, and often with very poorly de- 

 veloped cell -walls. These, too, have 

 already got or will shortly be given 

 names, although many of them are prob- 

 ably nothing more than development- 

 stages of the larger forms. We can 

 recognise the whole series by their char- 

 acteristic ring-furrow, so that we are 

 seldom left in doubt as to the classifica- 

 tion of even the simplest types. Still a 

 good deal remains to be done before we 

 With brown flagellate cells in the cau claim a thorough acquaintance with 

 ^4^0^ ^""jr^" ^f'"^"'^"'''^*'" their development-history and systematic 

 ' ' '^ " ' arrangement. 



The third series of pelagic algae consists of brown flagellates, 

 the chief place amongst which is occupied by calcareous 

 flagellates or coccolithophoridse (see Fig. 239). Their cells are 



Fig. 235 



Ornithocercus magnif/ccs. 



>:^^/^: 



Fig. 236. 



a, Citharistes apsteini (^-) ; b, Histioneis gubernaiis {-\^), both with cells of 



brown flagellates in special chambers. (Schiitt. ) 



generally nearly globular, with one or two cilia and one or two 

 brown chromatophores, and they are protected by remarkable 

 shields of lime which unite into a complete defensive covering, 

 though sometimes with a big opening in front. The cell does not 



