CHAPTER XXVII. 



BIONOMIC CLASSIFICATION OF PLANTS AND ANIMALS. 



A bionomic classification, or one based on the relationship of 

 the organism to its environment, cannot agree with one based en- 

 tirely on anatomic characteristics. It is a more primitive classifica- 

 tion, but a very useful one from many points of view. 



Subdivisions. 



Primary Divisions. The primary divisions of the organisms 

 agree with the primary divisions of the life districts, i. e., the 

 marine, fresh water, and atmospheric or terrestrial. We have, ac- 

 cordingly, Jialo-bios, liinno-bios, and atiiio-bios (geo-bios), each of 

 these including the plants and animals of the respective realms. 



Secondary Divisions. The next division is based on the rela- 

 tion of the organism to the substratum, where we have floating 

 types or plankton, swimming types or nekton, and bottom types 

 or benthos. The first two belong to the pelagic and abysso-pelagic 

 districts, the third to the littoral and abyssal. Their further sub- 

 divisions and relationships are as follows : 



1. Holoplankton: organisms spending all their 

 lives as plankton (ex., jelly fish). 



2. Meroplankton: organisms leading a plank- 

 tonic life during larval stages only (ex., 

 Crustacea, echinoderms, coelenterates). 



3. Pseudoplankton: organisms normally at- 

 tached but floating through accident, as 

 the Sargassum, leaves and trunks of trees, 

 or parts of dead organisms, such as shells of 

 molluscs, etc. 



4. Epiplankton: organisms living upon or at- 

 tached to floating objects (ex., Crustacea 

 and hydroids of the pseudoplanktonic Sar- 

 gassum ; Lepas attached to floating logs, etc. 



1. Holonekton. 



2. Meronekton. 



3. Epinekton: organisms parasitically or other- 

 wise attached to swimming or flying ani- 

 mals. 



991 



A. Plankton (floating or- 

 ganisms) 



B. Nekton (swimming or 

 flying organisms) .... 



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