S6 FRESH-WATER BIOLOGY 



Communities of different orders are given below with taxonomic 

 divisions of corresponding magnitude opposite for comparison. 

 With the exception of the first, these taxonomic groupings do not 

 bear the slightest relation to the ecological groupings, but are added 

 to indicate magnitude. 



Ecological Groups Taxonomic Groups 



(Mos) Mores Form (forms) (species) 



Consocies Genus 



Stratum or story Family 



Association or society Orde ■ 



Formation Class 



Extensive formation Phylum 



(Aquatic and terrestrial) (Vertebrates and invertebrates) 



Mores ^ are groups of organisms in full agreement as to physio- 

 logical life histories as shown by the details of habitat preference, 

 time of reproduction, reaction to physical factors of the environ- 

 ment, etc. The organisms constituting a mores usually belong to 

 a single species but may include more than one species or one 

 species may occupy two or more habitats and be made of several 

 mores (Shelf ord; Allee). 



Consocies are groups of mores usually dominated by one or two 

 of the mores concerned and in agreement as to the main features 

 of habitat preference, reaction to physical factors, time of repro- 

 duction, etc. 



Strata are groups of consocies and organisms not so grouped, 

 occupying the recognizable vertical divisions of a uniform area. 

 Strata are in agreement as to material for abode and general physi- 

 cal conditions but in less detail than the consocies which constitute 

 them; for example, the understone stratum of a rapid brook (see 

 Fig. s, p. 52). 



^ Mores (latin singular mos), "behavior," "habits," "customs"; admissible 

 here because behavior is a good index of physiological conditions and constitutes the 

 dominant phenomenon of a physiological life history and of community relations. 

 Tliis term is used just as form and forms are used in biology, in one sense to apply 

 to the general ecological attributes of motile organisms, in another sense to animals 

 or groups of animals possessing peculiar attributes. When apphed in this latter 

 sense to single animals or a single group of animals the plural is used in a singular con- 

 struction. This seems preferable to using the singular form mos which has a different 

 meaning and introduces a second word. The organism is viewed as a complex of 

 activities and processes and mores is therefore a plural conception. 



