ECOLOGICAL SUCCESSION. 33 



natural history generalization consists in discovering that certain 

 habits are characteristic of a few known (as to habits) members 

 of a given taxonomic group of animals, in striking a sort of 

 general average of the known habits of the members in question 

 and putting such an average into the form of a general statement 

 to apply to all the group, known or unknown. Such generali/a- 

 tiiii- have their place in didactics, but they are the most in- 

 accurate phase of zoology. Though often used as a basis for 

 generali/ati"! rulizations based upon them have a i|tie>tion- 



able value. 



The crucial question before us is, then, ("an we, on the;>a>i>of 

 ecolo-jc.il succession or other natural ba-i-. classify and compare 



animal mores and make ^-nePali/alii >n- . ,n the ban- ol" >ueh 

 ( -la il"n ation .md comparison.' If in\ tion an-\\er- in 



the at!innati\ i . \\r may or^ani/e a general -\ -tern for the 

 < la--il"u aiion 1 material- \\hich -hall be -ufticiciitly 



independent of other method- and s\-tem- i .f cla--ilic.it ion \ 

 Bervi nu-aii- i.l" thn. \\iiii4 additimial li.^ht on the ^i-nerali/a- 



tioii- i,|" other / il field-. >urh a- ].h\-ioIo-\, lureditx, or 



evolution, Indeed, plant eCol(>Ki-t- ha\e ] -d laf with 



Midi a rla.--ilication i\\'arniin. ' 'OI, and main 



other-). Theiin -ill; - .in now re< < .-^iii/i <1 a- of much importance 

 l.\ l>otani>t- i:eiH rall\ . The lo^i, .md method Lack of their 

 ( la--i!n atioli i- the Bailie as ours. The dr 68 lie in the tact 



that dilleMiHe- in ph\ >iolo ;^ical make up in plants i- u-ually 



indicated \>\ vegetative J 'lilt ilituitint- in physiological 



make ii]> in animal- i- indicated \>\ dilh-n -in e- in // 



!". oi, ,-i( .il succession has i been -mdicd e\perinu-n- 



tall\. l-".\]ierimental >tndii->, if properly conducted, \\ill an>\\er 

 tin- c|iu-Mioii . ,f ili, signii of all the propositions here prc- 



>eiited. Such experimentation -lumld be conducted \\ itli reference 

 to an iittalyzt. :nl >hoiild con>ist of the comparison 



of the inimal- of different and of similar environments. 



\ . ^l \I\IAK\ . 



I. Fi-hc- ha\e detinite habitat preference:- which cati-e them 

 to be delinitcU arranged in >tream> which have a graded -eries 

 of condition^ from mouth to source. 



