ECOLOGICAL SUCCESSION. V, 



ol plan 1 - i- the important thing and is commonly indicated In- 

 growth lorm (superficially hut not finally) which is the index of 

 internal physiological state induced by the surrounding condi- 

 tion-. IMant formation- arc tlu- expression of the condition- ot" 

 exi-tence for the plants of a definite area. The formation i- the 

 fundamental unit of the ecology of communities and carries with 

 it no consideration of species whatever. Identical or similar forma- 

 tion- ottcn <lo not ha\'e a single specie-- in common. A- \\ e lia\ e 

 pointed out I.efore, species are of importancr only in -o far as 

 their e< ..logical constitutions are specific character-. It i- not 

 s /-" n-li that we are to expect to be a ociated with species 



of plant-, hut mores of fish with growth form in plant- or with 

 plain lormaiions. Furthermore, relation- to venation \\hich 

 are ot importance are to be expected primarily in connection 

 \\ ith breeding. 



iihjrction to ilu- use of vegetation as an index of tndition-. 

 due ID mi-apprehension, is to be expected. Ho\\e\er. \\hen the 

 theoretic.il probabilities are understood, \\ e have not the data 

 in the case ol li-h, with which to determine \\ he t her or not ^roictii- 



"i and more* are associated. The subject i- one for -pecial 

 experimental and observational investigation. 



In connection with the problems of animal heha\ ior, (hi- point 

 o| \ie\\ Dpen- up a field wherein the role of the different cn\ iron- 

 menial c..iiditioii- in the control of behavior m.i\ he -! tidied in 

 naiuie .1- \\ell as in experiment. As a background |..r the -tud\ 



"t all a-pet 1- "I behavior the point of \ie\\ here pre-ented -eelll- 



to < 'ii i dei ided advantages. 



Comparative study ol behavior from thi- point of \ie\\ ha- 

 heen impracticable because of a lack ot kno\\led-e ot en\ iron- 

 mem-. I mil \\e can accjiiire a knouled-^e and a nomenclature 

 that -hall he ^eneralK" understood the \\orker mu-i \\rite exten- 

 sive de-criptioit- of the environment, and i- likeK to eni])ha-i/e 

 detail- \\lii-h are of little important 



The acti\iiies of an animal (behavior are ..f greal economic 

 imporian.t. they determine distribution. The relation- ot the 

 hchdrior prohlcms and the distribution, the i/uuntitdtiir diid the eco- 

 nomic problems seem especially intimate, so that the investigation of 

 any one from this point of rie:c must contribute to all as well a- to 



