992 PRINCIPLES OF STRATIGRAPHY 



C. Benthos (bottom or- f i. Vagrant: with power to walk, crawl, or ] Littoral 



ganisms) I creep over the bottom. > and 



[ 2. Sedentary: Attached to the bottom. J Abyssal. 



According to the realm in wliich the organism Hves we have, 

 therefore : 



I. Marine or Halobios, including 



A. Haloplankton 



B. Halonekton 



C. Halobenthos 



II. Freshtvater or Limnobios, including 



D. Limnoplankton 



E. Limnonekton 



F. Limnobenthos 



III. Terrestrial or Atmohios (Geobios), including 



G. Atmoplankton 

 H. Atmonekton 

 I. Atmobenthos 



With reference to depth, we may further subdivide marine 

 plankton, etc., into anoplankton (from avw, upward*) or that 

 occurring above the lOO fathom-line; this may be divided into 

 anoholoplankton, anomeroplankton, anopseudoplankton and anoepi- 

 plankton. Below lOO fathoms we have the meso plankton (from 

 fieo-os, middle), and again, just above the abyssal depths may 

 occur the hypoplankton (from viro, under), anonekton, mesonek- 

 ton and hyponekton, as well as anobenthos (littoral district), meso- 

 benthos (bathyal district) and hypobenthos (abyssal district) may 

 also be recognized. 



Each of these divisions may now be considered in detail. 



A. Haloplankton. 



I. Haloplankton. The term plankton was introduced by Vic- 

 tor Hensen in 1887. It is derived from the Greek ;rXayKTos, which 

 means wandering or drifting about aimlessly. The true plankton, 

 or haloplankton, is most typically developed in the sea. It com- 

 prises those organisms which spend their lives in the sea drifting 

 about from place to place, without power to direct their own 



* The term epiplankton was proposed for this by George H. Fowler in 191 1 

 (Encyclopedia Britannica, nth ed., vol. xxi, p. 721), but was preoccupied by 

 Grabau in 1909 as above defined (3). Hence the names anoplankton and ano- 

 benthos are here proposed. The names mesoplankton, mesobenthos, hypo- 

 plankton and hypobenthos, also proposed by Fowler, are, however, acceptable. 



