ECOLOGICAL SUCCESSION. 29 



point of view of the compiler differs from that of the original 

 investigator. To illustrate principles and methods we have relied 

 upon compilation far more than could otherwise be justified. 

 Still certain facts and relation- appear to be clearly indicated 

 by tin- reconnaissance. These will be roughly grouped under 

 tin- head- quantitative, economic and general. 



i. (Jnantitntive. As has been pointed out in the body of the 

 paper, the quantity of living material in tin- form of plankton, 

 invertebrate-, and vegetation increases a- a pond '/rows eco- 

 lojcally older. In our data there an- t\\<> exception- to thU 

 which mu-i be noted: First the greater number of Kniomo-traca 

 in the younger ponds in early spring and the le er number in 

 pom I 5/ (in all occasions. The greater number in the early 

 .- prim: i- not ea-ily explained but may be due to the better con~ 

 ditioii- on the bottom where the egg-, etc.. <>f the plankton 

 Kiiiomo-ir.K a art- found. Possibly the larger areas of clean 

 bottom pre\eiit their being buried and shut a\va\ from the 

 eitei ' oi tin sun's heat, oxygen, etc. 



I'did 5. i-. as we have indicated, probablv not comparable mi 

 .K' cunt of the contamination; also plankton production i- mca- 

 Mired in < iii-tacea and Marsh ('03) ha- pointed cut pit ible 

 errors in thi- method. A study of all the plankton < -cii-t itueiii- 

 mi/In .-ho\\ a different relation of 5c. Here, however, low plank- 

 tcn content is associated with little COj (Birge and Juday, 'n . 



The iccied /ross vegetation secures necessary --ib- Irom the 

 -oil and I 'end '05) jxiintcd out that it im Tea-e- plankton bei ause 

 the foods absorbed from the soil are added to thewaterwhen the 

 plain- decay. Our results are then in full accord with tho-ed 

 l'cn-1. Se< al-o Hirge \' Juday, 'i I . Knauihe, '07, p. 57- 



The greater number of large invertebrate-, appears to I.,- gen- 

 erally clo.-elv related to the amount d" gross vegetation. .\Carl\- 

 all Mich animals cling in vegetation and main d the species 

 found in tlu- older ponds use the \e-ei.uion a- a m.-an- of reaching 

 the -nrface fcr air, of avoidii -unli-ht, and as breeding 



places. The majority of such animal- plan- their into or 



upon the plant-. Gross vegetation i- al-<> thickly covered \\ith 

 minute organisms \\hich afford Iced for many animal-. 



It i- probable that the amount of rooted vegetation in i-olated 



